Shared memory image forming system

ABSTRACT

An image forming system, wherein a second digital copying machine stores image data temporarily on behalf of a first digital copying machine at its request and returns the stored image data upon receipt of a return request. When the second digital copying machine has not received any return request from the first digital copying machine within a predetermined period, the second digital copying machine erases the stored image data to utilize its own memory efficiently.

FIELD OF THE INVENTION

The present invention relates to an image forming system comprising aplurality of image forming apparatus, such as digital copying machines,which are interconnected through a transmitting apparatus.

BACKGROUND OF THE INVENTION

A digital copying machine, an example commercialized image formingapparatus, reads an original image by means of an image read section toprocess the read original image in a specified manner by means of animage processing section, and prints out the processed image data bymeans of a recording section as a copy image. Thus, the digital copyingmachine of this type produces an image on a sheet using only the imageprocessing functions pre-installed therein.

On the other hand, an idea of forming a network by interconnecting aplurality of image recording apparatus or the like has been proposedrecently. For example, Japanese Laid-Open Patent Application No.116834/1978 (Tokukaisho 53-116834) discloses an arrangement tointerconnect a plurality of image reading apparatuses and a plurality ofimage recording apparatuses through a single control section.

This arrangement enables each image recording apparatus to output a copyof an original image read by any of the above image reading apparatuses.Thus, when more than one kind of document is copied, each kind ofdocument is set to a separate image reading apparatus and the copy ismade by a single image recording apparatus, thereby reducing an idletime of the image recording apparatus compared with a case where eachkind of document is set in a single image reading apparatus.

Also, Japanese Examined Patent Publication No. 36592/1995 (Tokukouhei7-36592) discloses an image forming system including a plurality ofcopying machines interconnected through a single control apparatus, andeach copying machine is furnished with an image read section and animage record section. In this system, image signals subject to recordingare distributed to more than one copying machine according to aspecified copying mode, so that those who received the image signals cancarry out the copying operation in parallel.

However, the above conventional image forming systems has a number ofproblems.

To begin with, each image processing function of the digital copyingmachine depends on a software program, which has been developed at anincreasing pace. Thus, the image processing function is upgraded in ashort period and new models with additional functions have been steadilycommercialized. Therefore, the state-of-the-art digital copying machinewith desired image processing functions becomes an outdated model withrelatively low level functions as soon as the user purchases it.

Because the user can neither upgrade the functions of his digitalcopying machine nor simply add new functions, if he wants higher levelor new functions, he has to purchase a new model. This is an economicburden for the user and a manufacturers' problem accompanying with theirefforts in always meeting users' demands.

The same can be said about a memory capacity of the digital copyingmachine. To be more specific, most of the higher level image processingfunctions, such as an electronic RDH (Recycle Document Handler)function, are feasible only when the digital copying machine has a largememory.

A possible solution to the above problem would be interconnectingcopying machines through a transmitting apparatus to enable them toshare their memories, a practical arrangement of which, however, has notbeen discussed in any of the prior art documents.

In addition, suppose that a first copying machine requests a secondcopying machine to store the transmitted data on its behalf, then, thesecond copying machine eventually accumulates a great volume of imagedata for a considerable period unless the first copying machine issues areturn request of the image data. Thus, the memory of the second copyingmachine is occupied by the image data from the first copying machine.This limits the memory function of the second copying machine, in otherwords, this causes an insufficient memory at the second copyingmachine's end, thereby hindering the full performance of the secondcopying machine.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an imageforming system, in which an image processing apparatus can share itsmemory with another image processing apparatus while reducing thecapacitive burden of the shared memory.

The above object is fulfilled by an image forming system furnished witha first image forming apparatus, a second image forming apparatus, and atransmitting apparatus for connecting the first and second image formingapparatuses for mutual image data transmission, wherein,

(1) the first image forming apparatus includes:

a recording section for forming a visible image based on image data;

a command input section for inputting an action command; and

a control section for transferring the image data from the first imageforming apparatus to the second image forming apparatus through thetransmitting apparatus at a command, inputted through the command inputsection, to issue a store request to the second image forming apparatusto store the image data on behalf of the first image forming apparatus,and

(2) the second image forming apparatus includes:

a storage section for storing image data;

a control section for storing the transferred image data from the firstimage forming apparatus into the storage section, and for returning thestored image data to the first image forming apparatus through thetransmitting apparatus at a return request issued by the first imageforming apparatus; and

an erasing section for erasing the stored image data in the storagesection.

When the first image forming apparatus reads a document of plurality ofpages using, for example, the electronic RDH (Recycle Document Handler)function, a data volume may exceed a capacity of the memory thereof insome cases.

However, the above arrangement can solve this problem. To be morespecific, the operator inputs a command into the first image formingapparatus through the command input unit, directing the same to requestthe second image forming apparatus to store the image data on itsbehalf. Upon receipt of such a command, the control unit of the firstimage forming apparatus starts to transfer the image data to the secondimage forming apparatus through the transmitting apparatus. The imagedata can be transferred either partially or entirely.

Then, the second image forming apparatus stores the transferred imageinto its storage unit, and returns the stored image data to the firstimage forming apparatus upon receipt of the return request therefrom.

The first image forming apparatus processes the returned image datausing specified functions and supplies the processed image data to therecording unit, which outputs the supplied image data in the form of avisible image.

According to the above arrangement, the first image forming apparatuscan process the image data while using the storage unit of the secondimage forming apparatus.

If the first image forming apparatus has not issued the return requestfor a considerable period, the transferred image data are accumulated inthe storage unit of the second image forming apparatus. Under theseconditions, the memory of the second image forming apparatus eventuallybecomes insufficient, thereby causing some trouble in its operation.

To eliminate this problem, the erasing unit erases the image data in thestorage unit as occasion demands.

Therefore, in the present image forming system, the first image formingapparatus can use the storage unit of the second image forming apparatuswhile eliminating operation troubles possibly causing at the secondimage forming apparatus's end.

For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart detailing an operation of an image forming systemin accordance with an example embodiment of the present invention;

FIG. 2 is a longitudinal section of a digital copying machine in theabove image forming system;

FIG. 3 is a block diagram depicting a structure of an image processingsection in the above digital copying machine;

FIG. 4 is a block diagram depicting a structure of control mechanism ofthe above digital copying machine;

FIG. 5 is a front view of a control panel of the above digital copyingmachine;

FIG. 6(a) is a front view showing a basic screen of a liquid crystaldisplay device in the above control panel;

FIG. 6(b) is a front view showing a first function setting screen;

FIG. 6(c) is a front view showing a second function setting screen;

FIG. 7(a) is a front view showing an image quality setting screen of theliquid crystal display device in the above control panel;

FIG. 7(b) is a front view showing a post-processing operation settingscreen of the liquid crystal display device in the above control panel;

FIG. 8(a) is a front view showing an initial setting screen of theliquid crystal display device in the above control panel;

FIG. 8(b) is a front view showing a finger print registration screen ofthe liquid crystal display device in the above control panel;

FIG. 8(c) is a front view showing a department management setting screenof the liquid crystal display device in the above control panel;

FIG. 9(a) is a front view showing a limiter setting screen of the liquidcrystal display device in the above control panel;

FIG. 9(b) is a front view showing a simulation screen of the liquidcrystal display device in the above control panel;

FIG. 10 is a diagram of the screens of the liquid crystal display devicein the above control panel;

FIG. 11 is a view explaining a schematic structure of the above imageforming system;

FIG. 12(a) is a front view of the first function setting screen of theliquid crystal display device in the control panel of FIG. 6(b) when theoperator has selected image edit functions he wishes to use;

FIG. 12(b) is a front view of the above liquid crystal display device inthe control panel after an italic function is selected;

FIG. 12(c) is a front view of an italic setting screen of the aboveliquid crystal display device in the control panel;

FIG. 13(a) is a front view of the second function setting screen of theliquid crystal display device in the control panel of FIG. 6(c) when theoperator has selected an image edit function he wishes to use;

FIG. 13(b) is a front view of the above liquid crystal display device inthe control panel when S4 of FIG. 15 is being carried out;

FIG. 13(c) is a front view of a sharpness setting screen of the aboveliquid crystal display device in the control panel;

FIG. 14 is a front view showing the above liquid crystal display devicein the control panel when S14 of FIG. 15 is being carried out;

FIG. 15 is a flowchart detailing an operation of the image formingsystem of FIG. 11 when a first image forming apparatus requests a seconddigital copying machine to carry out image processing on its behalf;

FIG. 16 is a flowchart detailing an operation of the image formingsystem of FIG. 11 when the first image forming apparatus issues a storerequest to the second image forming apparatus to store the image data onits behalf;

FIG. 17(a) is a front view of the above liquid crystal display device inthe control panel when S37 of FIG. 16 is being carried out;

FIG. 17(b) is a front view of the above liquid crystal display device inthe control panel after an external memory key of FIG. 17(a) is pressed;

FIG. 17(c) is a front view of the above liquid crystal display device inthe control panel after a continue key is pressed;

FIG. 18 is a flowchart detailing an operation of an image forming systemin accordance with another example embodiment of the present invention,and it details an operation of erasing image data stored on behalf ofanother digital copying machine at its request;

FIG. 19 is a front view showing the above liquid crystal display devicein the control panel when S69 of FIG. 18 is being carried out;

FIG. 20 is a flowchart detailing an operation of an image forming systemin accordance with a further example embodiment of the presentinvention, and it details an operation of erasing image data stored onbehalf of another digital copying machine at its request;

FIG. 21 is a flowchart detailing an operation of an image forming systemin accordance with still another example embodiment of the presentinvention, and it details an auto-clear operation of image data storedon behalf of another digital copying machine at its request;

FIG. 22 is a view explaining a schematic structure of an image formingsystem in accordance with still another example embodiment of thepresent invention;

FIG. 23 is a view explaining a schematic structure of an image formingsystem in accordance with still another example embodiment of thepresent invention;

FIG. 24 is a view explaining a schematic structure of an image formingsystem in accordance with still another example embodiment of thepresent invention;

FIG. 25 is a front view illustrating a liquid crystal display device ina control panel of a digital copying machine in the image forming systemof FIG. 24 when displaying transfer history data;

FIG. 26 is a flowchart detailing a memory operation in the image formingsystem of FIG. 24; and

FIG. 27 is a flowchart further detailing the memory operation of FIG.26.

DESCRIPTION OF THE EMBODIMENTS

(Embodiment 1)

Referring to FIGS. 1-17, the following description will describe anexample embodiment of the present invention.

An image forming system of the present embodiment comprises a pluralityof digital copying machines interconnected through a transmittingapparatus. FIG. 2 is a cross section showing an entire structure of adigital copying machine 30 as an example of the above digital copyingmachine. As shown therein, the digital copying machine 30 includes ascanner section 31, a laser printer section 32 serving as recordingmeans, and a post-processing operation device 34 having a sorter.

The scanner section 31 includes a document table 35 made of transparentglass, an RADF (Recirculating Automatic Document Feeder) 36 forautomatically feeding documents to the document table 35, and anoriginal image read unit, that is, a scanner unit 40 for reading anoriginal image of a document set on the document table 35 throughscanning. The original image read by the scanner unit 40 is sent to animage processing section, which will be described below, in the form ofimage data to be processed in a specified manner.

The RADF 36 is a device for automatically feeding a pile of a documentset on an attached document tray to the document table 35 per sheet. TheRADF 36 includes a transportation path for a one-side document and atransportation path for a two-side document as well as transportationpath switching mechanism, so that the scanner unit 40 can read eitherside or both sides of the document at operator's choice.

The scanner unit 40 includes a first scanning unit 40a, a secondscanning unit 40b, an optical lens body 43, and a CCD (Charge CoupledDevice) 44. The first scanning unit 40a is composed of a lamp reflectorassembly 41 for scanning a sheet of the document on the document table35 by irradiating light on the sheet surface, and a first reflectingmirror 42a.

The second scanning unit 40b is composed of a second reflecting mirror42b and a third reflecting mirror 42c. The first through thirdreflecting mirrors 42a-42c are provided to guide light reflected fromthe sheet of the document to the CCD 44. The optical lens body 43 formsan image on the CCD 44 by converging the reflected light thereon, andthe CCD 44 is an element which converts the image formed by thereflected light into an electric image signal.

The scanner section 31 reads an original image to convert the same intoimage data by the link-up operation of the RADF 36 and scanner unit 40.More specifically, while the RADF 36 steadily feeds the document persheet onto the document table 35, the scanner unit 40 reads the originalimage on each sheet by moving back and forth along the bottom surface ofthe document table 35.

The image data obtained by the scanner unit 31 are sent to the imageprocessing section to be processed in various manners as specified, andthe processed image data are temporarily stored in a memory 73 therein,which will be described in detail below. Subsequently, the image dataare supplied to the laser printer section 32 at an output command, andrecorded on a sheet in the form of an image.

The laser printer section 32 includes a laser writing unit 46 and anelectrophotographic processing portion 47 for forming an image in itsupper half region, and a sheet containing.transporting portion 55 in itslower half region. The laser writing unit 46 includes a semiconductorlaser for emitting a laser beam in response to the image data from thememory 73, a polygonal mirror for deflecting the laser beam at isometricspeed, an f-θ lens for correcting the above deflected laser beam to bedeflected at a constant velocity on a photosensitive drum 48 of theelectrophotographic processing portion 47, etc.

The electrophotographic processing portion 47 is arranged in a knownmanner, that is, the same includes the photosensitive drum 48, andaround which a charger, a developer, a transferring device, a separator,a cleaner, a fuser 49, etc. are provided. A transportation path 50 isformed in the downstream side of the fuser 49 with respect to adirection in which a sheet is transported to have an image formedthereon. The transportation path 50 branches into two paths: atransportation path 57 and a transportation path 58 that communicatewith the post-processing operation device 34 and sheetcontaining.transporting portion 55, respectively.

The sheet containing.transporting portion 55 includes a first cassette51, a second cassette 52, a two-side copying unit 53, and a multi-manualtray 54. The first and second cassettes 51 and 52 contain piles ofsheets of different sizes, respectively. When the operator selectseither cassette containing the sheets of the desired size, the sheetsare steadily fed to the electrophotographic processing portion 47 one byone from the top of the pile in the selected cassette. The two-sidecopying unit 53 supplies a sheet having formed an image thereon to theelectrophotographic processing portion 47, either directly or afterturning the sheet over.

In the laser printer section 32, the image data retrieved from thememory 73 are outputted from the laser writing unit 46 in the form of alaser beam to form an electrostatic latent image on the surface of thephotosensitive drum 48 in the electrophotographic processing unit 47.Then, the electrostatic latent image is turned into a visible tonerimage, which is electrostatically transferred onto a sheet transportedfrom the sheet containing.transporting portion 55 and fused thereon bythe fuser 49.

After the image is formed thereon, the sheet is sent to thepost-processing operation device 34 from the fuser 49 through thetransportation path 50, or supplied again to the electrophotographicprocessing portion 47 through the transportation paths 50 and 58 andtwo-side copying unit 53.

Next, the image processing section of the digital copying machine 30will be explained. The image processing section processes the image dataof the document sent from the scanner unit 31. As shown in FIG. 3, theimage processing section includes an image data input portion 70, animage data processing portion 71, an image data output portion 72, theabove-mentioned memory 73 serving as storage means, and a PCU (PrintControl Unit) 74 serving as control means.

The digital copying machine 30 is under the control of the PCU 74, whichis composed of a CPU (Central Processing Unit). The memory 73 iscomposed of a RAM (Random Access Memory), a hard disk, etc., to storethe image data.

The image data input portion 70 includes a CCD part 70a, a histogramprocessing part 70b, and an error diffusion processing part 70c. Theimage data input portion 70 converts the image data of the originalimage read by the CCD 44 into binary data, and makes a histogram ofdigital amount of the binary data to process the image data through theerror diffusing method, and stores the resulting data into the memory 73temporarily.

The CCD part 70a converts an analog signal representing the contrast ofeach pixel in the image data into a digital signal, and subsequentlycarries out an MTF (Modulation Transfer Function) correction, ablack-and-white correction, or a gamma correction on the digital signal.Then, the CCD part 70a outputs the resulting 256-level (8-bit) digitalsignal to the histogram processing part 70b.

The histogram processing part 70b produces contrast data (histogramdata) by adding up the digital signal outputted from the CCD part 70aseparately in the 256-level pixel contrast. The histogram data thusobtained are sent to the error diffusion processing part 70c, or to thePCU 74 when occasion demands as pixel data.

The error diffusion processing part 70c employs the error diffusingmethod known as a method of pseudo-half-tone processing. To be morespecific, an error caused by converting a pixel into binary data isreflected when converting the adjacent pixels into binary data. Thus, an8-bit/pixel digital signal outputted from the CCD part 70a is convertedinto 1-bit (binary data) digital signal and a redistribution computationis carried out to produce a copy image rendering contrast as true as toan original in any specific region.

The image data processing portion 71 includes a multi-value processingparts 71a and 71b, a synthesis processing part 71c, a contrastconversion processing part 71d, a scaling processing part 71e, an imageprocessing part 71f, and an error diffusion processing part 71g, and acompression processing part 71h. The image data processing portion 71 isa processing portion that converts input image data into image data theoperator desires. Thus, the input image data are processed by the imagedata processing portion 71 until the final output image data are storedin the memory 73. Note that, however, the aforementioned processingparts in the image data processing portion 71 are arranged to operateseparately only when occasion demands.

The multi-value processing parts 71a and 71b convert the binary imagedata from the error diffusion processing part 70c into 256-level data.The synthesis processing part 71c carries out a logical computation forevery pixel, in other words, it selectively computes an OR, an AND, andan exclusive-OR. The data subject to the logical computation are theimage data stored in the memory 73 and bit data from a pulse generator(PG).

The contrast conversion processing part 71d sets an arbitraryrelationship between the input contrast and output contrast for the256-level data based on a predetermined level converting table. Thescale processing part 71e carries out interpolation processing for adesignated magnification based on the known input data to compute thepixel data (contrast value) of the subject pixel after the scaling.Subsequently, the image data are scaled in the sub-scanning directionfirst, and thence in the main scanning direction based on the pixel datathus computed.

The image processing part 71f processes the input image data in variousmanners, and collects data related to data array to extract the featureand the like. The error diffusion processing part 71g operates in thesame manner as the error diffusion processing part 70c in the image datainput portion 70. The compression processing part 71h compresses thebinary data by a coding method known as the run-length. Note that thecompression processing part 71f compressed the final output image in thefinal processing loop.

The image data output portion 72 includes a restoring part 72a, amulti-value processing part 72b, an error diffusion processing part 72c,and a laser beam output part 72d. The image data output portion 72restores the compressed image data stored in the memory 73 to the256-level data, and diffuses the error in quaternary data which, whenformed into an image, renders a smoother half-tone representation thanthe one formed by the binary data, after which the image data outputportion 72 transfers the resulting data to the laser beam output part72d.

The restoring part 72a restores the data compressed by the compressionprocessing part 71h. The multi-value processing part 72b operates in thesame manner as the multi-value processing parts 71a and 71b in the imagedata processing portion 71. The error diffusion processing part 72coperates in the same manner as the error diffusion processing part 70cin the image data input portion 70.

The laser beam output part 72d converts the digital image data into alaser ON/OFF signal based on a control signal from an unillustratedsequence controller. The semiconductor laser in the laser writing unit46 comes on or goes off based on the above ON/OFF signal to write anelectrostatic latent image on the photosensitive drum 48.

The data entering into the image data input portion 70 and coming outfrom the image data output portion 72 are, as a general rule, stored inthe memory 73 in the form of binary data to reduce an occupied space.However, the data may be stored in the form of quatanary data tomaintain the quality thereof.

As has been explained, the PCU 74 controls the overall operation of thedigital copying machine 30, and the control mechanism of the PCU 74 isillustrated in FIG. 4.

As shown in the drawing, the PCU 74 is connected to a disk-related load75, an RADF-related load 76, a control substrate unit 77, a sortercontrol unit 78, a scanner-related load 79, a printer-related load 80,and the above-mentioned image data processing portion 71.

The PCU 74 manages the foregoing components separately using thesequence control by outputting a control signal to each. Thedisk-related load 75 is a load of the components other than the digitalcopying machine 30 main body, that is, a load of the motor of the sorterin the post-processing operation device 34, a clutch, etc. TheRADF-related load 76 is a load of the motor, clutch, switch, etc. of theRADF 36. The scanner-related load 79 is a load of the motor, solenoid,etc. of the scanner unit 40. The printer-related load 80 is a load ofthe motor, solenoid, high-voltage power source, etc. of theelectrophotographic processing portion 47. The sorter control unit 78includes a CPU and controls the operation of the sorter based on thecontrol signal from the PCU 74.

The control substrate unit 77 is an input section including a CPU,through which the operator sets a copying mode and the like or enters acommand in the digital copying machine 30. The control substrate unit 77transfers a control signal to the PCU 74 in response to the operator'sinput. For example, when the operator sets a copying mode, the PCU 74controls the digital copying machine 30 to operate in the set mode usingthe above control signal. On the other hand, the PCU 74 transfers acontrol signal indicating the operating condition of the digital copyingmachine 30 to the control substrate unit 77. The control substrate unit77 displays the current operating condition of the digital copyingmachine 30 on the display portion in response to the above controlsignal, thereby enabling the operator to confirm the current operatingcondition.

The memory 73, connected to the image data processing portion 71, iscomposed of a main memory 73a made of, for example, a semiconductormemory, and a hard disk 73b. An image data transmitting unit 81,connected to the main memory 73a, is provided to allow the mutualtransmission between the digital copying machine 30 and the otherdigital data apparatuses with respect to the image data, image controlsignal and the like. The image data transmitting unit 81 corresponds,for example, an interface 93a and a transmission line 96 in a digitalcopying machine 93 of FIG. 11.

The control substrate unit 77 includes a control panel 90 of FIG. 5 ascommand input means. The control panel 90 includes a touch panel typedisplay portion at the center as a liquid crystal display device 1. Ascreen switch command area 1a is formed in a part of the screen of theliquid crystal display device 1. The screen switch command area 1a isprovided to enable the operator to input a command to switch a displayscreen to a screen for selecting an image edit function he wishes touse. Although it will be described in detail below, when the operatordirectly presses the screen switch command area 1a with his finger, alist of edit functions is displayed on the screen of the liquid crystaldisplay device 1 to enable the operator to select his desired editfunction. Thus, the operator can set his desired edit function only bypressing the corresponding region on the display area with his finger.

As shown in FIG. 5, the control panel 90 includes a dial 2 at the leftedge for controlling the brightness of the screen of the liquid crystaldisplay device 1. A magnification auto-setting key 3, a set of zoom keys4, two fixed magnification keys 5 and 6, and a 1× (equal size) key 7 areprovided between the dial 2 and liquid crystal display device 1. Theoperator presses the magnification auto-setting key 3 when he wishes toset the digital copying machine 30 into a mode, in which an adequatecopy magnification is automatically selected, and either zoom key 4 whenhe wishes to increase or decrease a copy magnification per 1%. Theoperator presses the fixed magnification key 5 or 6 when he wishes toselect a fixed magnification, and the 1× key 7 when he wishes to reset acurrent copy magnification to the standard magnification (that is,100%).

Also as shown in FIG. 5, the liquid crystal display device 1 includes aset of copy quantity keys 13, a clear key 14, a start key 15, an allclear key 16, an interruption key 17, a manipulation guide key 18, amessage advancing key 19, a memory transmitting mode key 20, acopy/facsimile switching key 21, and a set of one-touch dial keys 22.

The operator presses the copy quantity key(s) 13 when he sets thedesired copy quantity, and the clear key 14 when he wishes to reset thecopy quantity or stop the continuous copying operation. The operatorpresses the start key 15 to start the copying operation, and the allclear key 16 when he wishes to reset all the set modes to standard. Theoperator presses the interruption key 17 when he wishes to make a copywhile a continuous copying operation is being carried out, and themanipulation guide key 18 when he needs some help in manipulating thedigital copying machine 30. When the manipulation guide key 18 ispressed, the manipulation instructions of the digital copying machine 30are displayed on the liquid crystal display device 1. The operatorpresses the message advancing key 19 when he wishes to advance themessages displayed in response to the operator's pressing of themanipulation guide key 18.

The memory transmission mode key 20 and copy/facsimile mode switchingkey 21 are the set keys related to a facsimile mode. The operatorpresses the memory transmission mode key 20 when he wishes to send thedocument data after the document data are stored in the memory. Theoperator presses the copy/facsimile mode switching key 21 when he wishesto switch the digital copying machine 30 from the copy mode to thefacsimile mode and vice versa. Each one-touch dial key 22 is arranged toremember a telephone number, so that the operator can make a phone callto a desired correspondent by a one-touch manipulating action.

The above is an example arrangement of the control panel 90 as to thekinds and alignment of the keys, and the control panel 90 may bemodified depending on the model of its own digital copying machines 30.

The above liquid crystal display device 1 can display, for example, abasic screen of FIG. 6(a), a first function setting screen of FIG. 6(b),a second function setting screen of FIG. 6(c), an image quality settingscreen of FIG. 7(a), a post-processing operation setting screen of FIG.7(b), an initial setting screen of FIG. 8(a), a finger printregistration screen of FIG. 8(b), a department management setting screenof FIG. 8(c), a limiter setting screen of FIG. 9(a), and a simulationscreen of FIG. 9(b), as well as the other screens explained below.

The basic screen includes six areas: a function setting area, an imagequality setting area, a post-processing operation setting area, aninitial setting area, a set function confirmation manipulation area, anda cassette setting area, which are denoted as setting keys 101a-101f,respectively. The basic screen can additionally display the cassette,contrast, copy quantity, and magnification that have been set. When theoperator manipulates the set function confirmation manipulation area,all the functions currently set in the present image forming system aredisplayed on the liquid crystal display device 1.

The first function setting screen includes six areas for setting editfunctions: mirror image, italic, inverse, shadow, trimming, and masking,which are denoted as setting keys 102a-102f, respectively. Further, thefirst function setting screen includes two control areas: one forreturning to the basic screen and the other for advancing to the nextpage screen. As soon as the operator presses the next page area, thescreen switches to the second function setting screen.

The second function setting screen includes four areas: the first andsecond ones for setting edit functions, namely, synthesis andindependent scaling, respectively; the third one for setting a sharpnessfunction to highlight the image; and the fourth one for setting atranslation function, which are denoted as setting keys 103a-103d,respectively. Further, the second function setting screen also includestwo control areas: one for returning to the basic screen and the otherfor returning to the previous page.

The image quality setting screen includes eight areas for setting thecontrast, HI-FI mode (high-quality copying mode), background eliminationmode, auto-scaling mode, text mode, text-picture mix mode, picture mode,and magnification. Further, the image quality setting screen displaysthe contrast and magnification that have been set.

The post-processing operation setting screen includes an input area forspecifying whether the document is one-sided or two-sided, another inputarea for specifying whether a copy is one-sided or two-sided, and anarea for setting a bookbinding function. The post-processing operationsetting screen further includes three areas for setting post-processingfunctions, namely, staple sorter, sorter, and finishing, as well as anarea for setting the RDH (Recycle Document Handler) function.

The initial setting screen includes six mode setting areas: a fingerprint registration mode, a department management mode, a simulationmode, a maintenance management mode, a new function registration mode,and an output device selection mode. In addition, the initial settingscreen includes a control area for returning to the basic screen.

The finger print register screen includes two input areas for inputtinga department code and individual's name, respectively. As soon as theoperator inputs the department code and individual's name, the inputdata are displayed in their respective input areas.

The department management setting screen includes several input areas,for example, one for setting a department code, and another for settingthe number of staff members in the concerned department. As soon as theoperator inputs the department code and the number of staff members andthe like, the input data are displayed in their respective input areas.

The foregoing screens switches as shown by the diagram of FIG. 10. Tobegin with, the liquid crystal display device 1 displays the basicscreen, and as soon as the operator presses one of the function settingarea, image-quality setting area, post-processing operation settingarea, and initial setting area, the basic screen switches to the screencorresponding to the pressed area.

For example, if the operator presses the function setting area, thebasic screen switches to the first function setting screen. Further, ifthe operator presses the control area for advancing to the next pagescreen, the first function setting screen switches to the secondfunction setting screen (NEXT function setting screen). On the otherhand, if the operator presses the control area for returning to thebasic screen, the first function setting screen returns to the basicscreen. If the operator presses the italic function setting area andinverse function setting area on the first function setting screen, boththe italic function setting area and inverse function setting area aredisplayed with a reversed background as shown in FIG. 12(a), and thefirst function setting screen switches to the one illustrated in FIG.12(b). When the operator presses an execute key 112a on the screen ofFIG. 12(b), the screen of FIG. 12(b) switches to the italic settingscreen illustrated in FIG. 12(c). The italic setting screen includes atilting angle input key 106a as a tiling angle setting area, and asetting end key 106b as a setting end input area. Further, the italicsetting screen displays an example capital letter A tilted by the setangle.

Note that, as soon as the operator presses any function setting area inthe first and second function setting screens, the screen switches to acorresponding parameter setting screen, such as the above italic settingscreen.

Here, example image edit functions available in the present imageforming system by manipulating the setting areas as explained above andthe effect of each are set forth in Table 1 below. Note that, however,the image edit functions are not limited to the examples specifiedbelow, and a function for making fair copies of handwritten charactersand/or pictures is also a possible option.

                  TABLE 1                                                         ______________________________________                                        IMAGE EDIT FUNCTION                                                                          EFFECT                                                         ______________________________________                                        INDEPENDENT SCALING                                                                          SET MAGNIFICATION IN LATERAL                                                  AND LONGITUDINAL                                                              DIRECTIONS INDEPENDENTLY                                       SHARPNESS      ADJUST IMAGE QUALITY                                                          OF A COPY                                                      BINDING MARGIN LEAVE AN ARBITRARY BINDING                                                    MARGIN                                                         FRAME ELIMINATION                                                                            ELIMINATE FRAME IN A COPY                                      CENTERING      MAKE A COPY AT THE CENTER                                                     OF A SHEET                                                     1-SET-2-COPY   MAKE A COPY OF A BOOK                                          ADDRESSED COPY SYNTHESIZE AN ADDRESS WITH                                                    A COPY                                                         MULTI-SHOT     COMBINE MULTIPLE PAGES IN                                                     ONE COPY                                                       TRIMMING       TRIM OFF A NON-DESIGNATED                                                     AREA                                                           MASKING        MASK A DESIGNATED AREA                                         MOVE           MOVE AN IMAGE TO AN                                                           ARBITRARY POSITION IN A COPY                                   SYNTHESIS      SYNTHESIZE MORE THAN ONE                                                      IMAGE                                                          MONOCHROMIC INVERSE                                                                          REVERSE NEGATIVE/POSITIVE IN                                                  A COPY                                                         CROSSHATCH/SHADE                                                                             CROSSHATCH/ SHADE AN IMAGE                                                    OR ISOLATE AN IMAGE                                                           ON CROSSHATCHED/SHADED                                                        BACKGROUND                                                     SHADOW         ADD SHADOW TO AN IMAGE                                         OUTLINE        BORDER AN IMAGE                                                ITALIC         TILT AN IMAGE                                                  MIRROR IMAGE   REVERSE AN IMAGE AS A                                                         MIRROR DOES                                                    REPEAT COPY    MAKE MULTI-COPY OF AN IMAGE                                                   IN ONE SHEET                                                   2-IN-1-COPY    MAKE ONE COPY OUT OF TWO                                                      SHEETS OF DOCUMENT                                             DATED COPY     ADD THE DATE TO A COPY                                         CENTER MARK    ADD A CENTER MARK TO A COPY                                    ENLARGE/DIVIDE DIVIDE AN ENLARGED COPY INTO                                   OUTPUT         A NUMBER OF SHEETS                                             TRANSLATION    TRANSLATE A DOCUMENT                                           HIGH-QUALITY   MAKE A HIGH-QUALITY COPY                                       PROCESSING                                                                    ______________________________________                                    

As shown in FIG. 11, the present image forming system comprises digitaldata machines installed in a typical office. To be more specific, thepresent image forming system includes three image forming apparatusesrespectively denoted as digital copying machines 91-93, a scanner 94,and a printer 95.

The digital copying machine 91 is an inexpensive, low-grade,"memoryless" model furnished with basic edit functions only."Memoryless" referred herein means that the machine does not include apage memory capable of storing a great volume of image data, butincludes at least a line memory which is sufficient to operate as anormal digital copying machine. Also, the basic edit functions means,for example, the monochromic inverse function that can be carried outwithout using a page memory. The digital copying machine 91 includes thescanner unit 40 of FIG. 2 with the resolution of 400 DPI in monochrome,and has a relatively low operating rate of 20 CPM (Copies Per Minute).The laser printer section 32 of the digital copying machine 91 has alsoa resolution of 400 DPI in monochrome, and includes an interface (I/F)91a.

The digital copying machine 92 is a middle-grade model whose scanner andprinter have a resolution of 400 DPI in monochrome, respectively, withan operating rate of 40 CPM. The digital copying machine 92 includesvarious kinds of edit functions, 64 M-byte memory (capable of storing upto four Japanese Standard A4 size papers at the resolution of 400 DPI,8-bit/pixel), and an interface 92a. The above memory corresponds to themain memory 73a of FIG. 4.

The digital copying machine 93 is a high-grade model whose scanner andprinter has a resolution of 400 DPI in monochrome, respectively with anoperating rate as high as 60 CPM.

Further, the digital copying machine 93 includes various kinds of editfunctions, a character recognition function, a bit data coding function,and a page memory of a capacity as large as 500M bytes (capable ofstoring up to 100 pages of Japanese standard A4 size papers at theresolution of 400 DPI, 8-bit/pixel at compression ratio of 1/4). Thus,the digital copying machine 93 can change the page order of the inputimage data, or store the document data in different formats. The abovememory corresponds to the main memory 73a and hard disk 73b of FIG. 4combined. The digital copying machine 93 also includes an interface 93a.

The scanner 94 can read a color image at a resolution of 600 DPI. Theprinter 95 can produce a color image copy at a recording density of 600DPI. The scanner 94 and printer 95 include interfaces 94a and 95a,respectively.

The digital copying machines 91 and 92, scanner 94, and printer 95 areconnected to the digital copying machine 93 through their interfaces91a-95a and transmission lines 96, thereby enabling mutual datatransmission. Thus, the interfaces 91a-95a, transmission lines 96, andPCU 74 of each digital copying machine constitute the transmittingapparatus herein.

The transmitting apparatus handles image data like bit data (forexample, level data per pixel unit: 8 bits in 256 levels), command dataand the like. The transmitting apparatus can transmit a high-level imagesuch as a landscape, at high definition. Also, the transmittingapparatus can reduce a volume of text data, namely, characters data, bycoding the read data, thereby enabling high-speed data transmission. Inparticular, the image data having different levels, for example, thoseof a landscape, are generally transmitted after reducing its volume bythe area leveling methods, such as the Dither method and error diffusingmethod. In case of the error diffusing method, each digital copyingmachine processes the image data prior to transmission, and sends theprocessed image data in an adequate format for any of the digitalcopying machines 91-93 and printer 95. Thus, when any of the abovedigital copying machines 91-93 receives the image data, thecorresponding machine inputs the received image data into its laserprinter unit 32 without converting the data format to convert the sameinto a writing data array by means of the image processing section andoutputs the resulting data.

Each of the interfaces 91a-95a is defined by their own prescribedprotocols and transmission rates, and an adequate standard is selectedbased on the content of the transmission data, such as a data volume,and the position of each machine in relation with the others, such as adistance. Further, in the present image forming system, the machines areconnected in one-to-one relationship, while at the same, some of themachines may be connected to the common transmission line 96 like adaisy chain. For this reason, each machine has its address, so that eachof the interfaces 91a-95a can identify a particular machine to which theimage data are addressed. The interfaces 91a-95a adopt, for example, anEthernet, for their standard, which are in effect a network permittinghigh-speed image data transmission. Alternatively, the interfaces91a-95a may adopt a general standard known as SCSI (Small ComputerSystem Interface) or RS-232C.

Each of the digital copying machines 91-93 includes a facsimilefunction, so that each can transmit data through a telephone line. Also,each of the digital copying machines 91-93 includes a printer mode, sothat each can print out document data sent from a personal computer orword processor.

The functions of the digital copying machine depend on its price, memorycapacity, and the like, and every office has different purpose anddemand. Thus, the digital copying machines are not limited to the aboveexample digital copying machines 91-93, and a great line-up of modelsare available.

Here, example image edit functions of the above digital copying machines91-93 of the present embodiment are tabulated for ready comparison inTable 2 below.

                  TABLE 2                                                         ______________________________________                                        IMAGE EDIT     MACHINE   MACHINE   MACHINE                                    FUNCTION       91        92        93                                         ______________________________________                                        INDEPENDENT    ∘                                                                           ∘                                                                           ∘                              SCALING                                                                       SHARPNESS                ∘                                                                           ∘                              BINDING MARGIN ∘                                                                           ∘                                                                           ∘                              FRAME          ∘                                                                           ∘                                                                           ∘                              ELIMINATION                                                                   CENTERING                ∘                                                                           ∘                              1-SET-2-COPY             ∘                                                                           ∘                              ADDRESSED COPY                     ∘                              MULTI-SHOT               ∘                                                                           ∘                              TRIMMING · MASKING                                                                            ∘                                                                           ∘                              MOVE                     ∘                                                                           ∘                              SYNTHESIS                          ∘                              MONOCHROMIC INVERSE                                                                          ∘                                                                           ∘                                                                           ∘                              CROSSHATCH/SHADE                                                              SHADOW · OUTLINE          ∘                              ITALIC · MIRROR IMAGE     ∘                              REPEAT COPY    ∘                                                                           ∘                                                                           ∘                              2-IN-1-COPY                        ∘                              DATED COPY · CENTER       ∘                              MARK                                                                          ENLARGE/DIVIDE                                                                OUTPUT                                                                        TRANSLATION                                                                   HIGH QUALITY                                                                  PROCESSING                                                                    ______________________________________                                    

The data related to these functions are stored in the memory 73 of eachof the digital copying machines 91-93, and the PCU 74 of each machinerefers these data when necessary.

In the present image forming system, the digital copying machine 93having the greatest number of image processing functions and largestmemory capacity is used as a second image forming apparatus, to whichthe other two digital copying machines 91 and 92, scanner 94, andprinter 95 are connected as shown in FIG. 11. This arrangement enablesthe copying machines 91 and 92 to use the image processing functions andmemory 73 of the digital copying machine 93. In case that the operator,manipulating the copying machine 91 or 92, wishes to use an imageprocessing function provided only to the digital copying machine 93, thedigital copying machine 91 or 92 sends the image data to the digitalcopying machine 93. Then, the digital copying machine 93 processes thereceived image data in a requested manner, and returns the processedimage data to the digital copying machine 91 or 92, whichever that hassent the original image data. Subsequently, the digital copying machine91 or 92 outputs the returned image data in the form of an image on asheet. In case that the digital copying machine 91 or 92 uses the memory73 of the digital copying machine 93, the digital copying machine 91 or92 sends the image data to the digital copying machine 93. Then, thedigital copying machine 93 stores the received image data into itsmemory 73, and returns the same, when occasion demands, to either thedigital copying machine 91 or 92, whichever that has sent the originalimage data.

The image processing operation of the image forming system arranged asabove will be detailed with reference to the flowchart of FIG. 15.Assume that the operator, manipulating the digital copying machine 91,selects the sharpness function to highlight an image in every certainnumber of pages, and the image data are distributed to the digitalcopying machines 92 and 93 for parallel processing herein. Note that thefunction setting screen of the liquid crystal display device 1 of thedigital copying machine 91 displays the functions provided to thedigital copying machines 92 and 93 as well. Also, note that theoperation of each digital copying machine is controlled by its own PCU74 unless otherwise specified.

To begin with, as soon as the operator presses the function setting key101a in the basic screen of the liquid crystal display device 1 of FIG.6(a), the screen switches to the first function setting screen of FIG.6(b). Then, the screen switches to the second function setting screen ofFIG. 6(c) when the operator presses the next page key. To select thesharpness function, the operator presses the sharpness key 103a in thesecond function setting screen (S1), then the sharpness function settingarea is displayed with a reversed background as shown in FIG. 13(a),which enables the operator to confirm that he has selected the sharpnessfunction.

Next, the PCU 74 of the digital copying machine 91 selects the digitalcopying machine(s) having the sharpness function within the imageforming system, and at the same time, compares the digital copyingmachines 91-93 in image processing performance (S2).

Then, the PCU 74 checks whether or not the sharpness function isprovided to its own digital copying machine 91 (S3). Since Table 2 abovereveals that the digital copying machine 91 does not have the sharpnessfunction, the checking result is negative in S3. Accordingly, the PCU 74displays the message "THIS MACHINE HAS NO SHARPNESS FUNCTION" on theliquid crystal display device 1, and directs the operator to selectwhether the job should be carried out by any other eligible devicewithin the system or not (S4). The display of the screen at this pointis illustrated in FIG. 13(b).

As has been described above, since the digital copying machine 91 doesnot have the sharpness function, if the operator wishes to continue thejob, the digital copying machine 91 has to request another machine tocarry out the sharpness function on its behalf. Herein, the digitalcopying machine 91 is arranged to confirm the operator's instruction bydisplaying the screen of FIG. 13(b). However, if the operator wishes tostop the job, he presses a cancel key 122b (S5), upon which the PCU 74cancels the set mode (S6).

On the other hand, when the operator presses a system selection key 122a(S5), the PCU 74 selects the digital copying machines 92 and 93 as thedevices having the sharpness function within the system. Also, thescreen of the liquid crystal display device 1 switches to the sharpnessfunction setting screen of FIG. 13(c).

Next, the operator inputs the desired highlighting level in sharpnessusing a sharpness input key 116a, and presses a setting end key 116b,upon which the digital copying machine 91 determines, to which of theselected digital copying machines it should issue a job request toprocess the document data (S7). Herein, as previously mentioned, boththe digital copying machines 92 and 93 are selected, and the detailedexplanation as to how digital copying machine 91 determines the mosteligible digital copying machine will be given below. Next, the digitalcopying machine 91 gives function control data to each image, andtransfers the same to the digital copying machines 92 and 93 afterscrambling the data, which also will be described below (S8).

The above image data are transmitted from the main memory 73a of FIG. 4of the digital copying machine 91 to both the digital copying machines92 and 93 through the image data transmission unit 81 and anunillustrated modem. The image data are transmitted together with thefunction control data composed of a processing code indicating therequested function, namely, the sharpness function herein. As shown inFIG. 11, the transmitted image data are inputted into the digitalcopying machines 92 and 93 through the interface 91a, transmission lines96, and interface 92a and 93a, respectively.

The image data processed herein are the data of the original image readby, for example, the scanner section 31. As previously mentioned, thedigital copying machine 91 does not include the page memory but the linememory alone. Therefore, the image data are read and transferredsteadily per line.

In case that the image data are transferred through a general network,the image data may leak to an external to the network. Thus, if thedocument contains confidential information, it is strongly recommendedto transmit the image data thereof with great care to prevent theleakage.

However, since anyone can access the general network at any time, anauthorized third party, or a so-called hacker, can easily access theimage data flowing through the network. Therefore, it is preferable tohave a preventive measure, such as scrambling the image data subject totransmission through the network, so that should the third party obtainthe image data, he can not make any sense out of them. In the presentembodiment, the image data are scrambled prior to transmission forprotection.

Upon receipt of the scrambled image data, the digital copying machines92 and 93 lift the scramble protection thereof, and confirm the same asbeing the image data and function control data specifying the requestedfunction. Accordingly, the digital copying machines 92 and 93 start toprocess the received image data using the sharpness function as wasrequested (S9).

Neither of the digital copying machines 92 and 93 returns the processedimage data to the digital copying machine 91 as soon as they end thejob. They withhold the processed image data until the digital copyingmachine 91 empties its own memory 73, in other words, until the digitalcopying machine 91 issues a return request for the processed image data(S10).

This is because, as previously mentioned, the digital copying machine 91does not have a memory of a sufficient capacity to store the processedimage data if they are returned immediately.

Upon receipt of the return request from the digital copying machine 91in S10, the digital copying machines 92 and 93 scramble the processedimage data and return the same to the digital copying machine 91 in adirection reverse to the previous inbound transmission (S11).

Then, the digital copying machine 91 lifts the scramble protection ofthe received image data (S12), which are steadily supplied to the laserprinter section 32 and outputted in the form of an image onto a sheet(S13). The recording operation is carried out in the same manner as wasexplained with the digital copying machine 30 above.

On the other hand, in case that the checking result is positive in S3,in other words, the digital copying machine that the operator ismanipulating has the sharpness function, a message is displayed on theliquid crystal display device 1 as shown in FIG. 14. In addition, thedigital copying machine directs the operator to decide whether he alsowishes to use any other eligible digital copying machine within thesystem by displaying a corresponding message on the liquid crystaldisplay device 1 (S14).

A good example of the above would be a case where the operator,manipulating the digital copying machine 92, wishes to use the sharpnessfunction by using the data processing portions 71 of both the digitalcopying machines 92 and 93.

Suppose again that the operator wishes to take the advantages of thepresent image forming system, in other words, he wishes to process theimage data using the digital copying machine 93 as well (S15). Then, thedigital copying machine 92 proceeds to S7, and selects any othereligible digital copying machine (herein machine 93) besides the self,and sends a part of the image data to the digital copying machine 93thus selected, so that the digital copying machine 93 proceeds to S8 andbeyond. At the same time, the digital copying machine 92 carries out thesharpness function on the rest of the image data. Note that the digitalcopying machine 92 may request the digital copying machine 93 to processall the image data on its behalf.

On the other hand, if the operator wishes to process the image datausing the digital copying machine 92 alone, the digital copying machine92 carries out the sharpness function on the image data (S16), andproceeds to S13 to output the processed image data.

As has been explained, in the present image forming system, if theoperator, manipulating the digital copying machine 91, wishes to use anedit function which is not provided therein, the digital copying machine91 requests both the digital copying machines 92 and 93 or either ofthem to process the image data on its behalf. Therefore, the digitalcopying machine 91 does not have to be a high-grade model like thedigital copying machine 92 or 93 furnished with various kinds of editfunctions.

In the example of FIG. 15, the digital copying machines 92 and 93 returnthe processed image data to the digital copying machine 91 at its returnrequest to enable the same to output a copy image in S11. However, adigital copying machine or printer may be selected under variousconditions, so that the processed image data are sent to the selecteddevice and outputted therefrom.

In the above explanation, only the digital copying machines 91-93 areconcerned. However, if the scanner 94 and printer 95 are combined, theycan operate in almost the same manner as a digital copying machine andcan be used as such. In this case, color image data read by the scanner94 with a resolution of 600 DPI are sent to the digital copying machine93 to be processed. Then, the digital copying machine 93 returns theprocessed image data with a recording resolution of 600 DPI to theprinter 95 to be printed out therefrom. Thus, the scanner 94 and printer95, when combined, can operate almost in the same manner as the abovedigital copying machines.

The present image forming system is arranged in such a manner that thedigital copying machines 91 and/or 92 can use the memory 73 of thedigital copying machine 93, which will be explained using exampletransmission where the digital copying machine 92, serving as the firstimage forming apparatus that issues a job request, and the digitalcopying machine 93, serving as the second image forming apparatus thatreceives the job request. Herein, the digital copying machine 92includes the electronic RDH function, and the job request referredherein is a request to store the image data on behalf of the digitalcopying machine 92, which is referred to as a store request hereinafter.

By the electronic RDH function, all the image data of a 10-page originaldocument are stored in the memory 73, and retrieved repetitively perpage to make, for example, 20 copies. The operator can select theelectronic RDH function by pressing the function set key 101a of FIG.6(a). As soon as the function set key 101a is pressed, an electronic RDHfunction setting key is displayed on the second function setting screenof FIG. 6(c).

The digital copying machine 92 includes a 64M-byte page memory as thememory 73. Thus, the memory 73 can store 256-level image data of up tofour Japanese Standard A4 size papers. This is sufficient for anordinary copying operation where a copy of the original document is madeafter the image data thereof are stored. However, in case that theoperator wishes to make several copies of a 10-page document using theelectronic RDH function, the image data of 6 pages exceeds the capacityof the memory 73. Thus, in this case, the electronic RDH function iscarried out using the memory 73 serving as the storage means of thedigital copying machine 93, which will be explained with reference tothe flowchart of FIG. 16.

To begin with, the operator selects the electronic RDH function in thedigital copying machine 92, and sets a 10-page document on the RADF 36of FIG. 2 (S31). Then, as soon as the operator presses the start key 15of FIG. 5 (S32), the steady document transportation from the RADF 36starts and an image on each page of the documents is successively readby the scanner unit 40. The image data thus produced are steadilyaccumulated in the memory 73 of the digital copying machine 92 (S33).Also, the above image data are subject to processing by the image dataprocessing section 71, such as the contrast conversion and scaling(S34). When the operator presses the electronic RDH function set key, anexternal memory selection key 121a is displayed on the liquid crystaldisplay device 1 together with an available memory indicating section121b as shown in FIG. 17(a).

While the scanner unit 40 is reading the document, if an availablecapacity of the memory 73 becomes insufficient to store the image dataof the rest of the document (S35), and if the operator has not pressedthe external memory selection key 121a in advance (S36), the liquidcrystal display device 1 displays a message warning that an externalmemory is necessary as is shown in FIG. 17(a) (S37).

As soon as the operator presses the external memory selection key 121a(S38), the screen switches to the one displaying a message as shown inFIG. 17(b). On the switched screen, the external memory selection key121a is displayed with a reversed background to indicate that the samehas been pressed, while the available memory indicating section 121bindicates a total of the available capacities of the memories 73 in boththe digital copying machines 92 and 93.

Next, when the operator presses the continue key 121c by following themessage displayed on the screen of FIG. 17(b) (S39), the digital copyingmachine 92 starts to transfer the image data to the digital copyingmachine 93 to store the same in the memory 73 thereof serving as anexternal memory (S40).

Then, the screen of the liquid crystal display device 1 switches to theone shown in FIG. 17(c). Note that the image data transferred to thedigital copying machine 93 are either the image data being read by thescanner unit 40 or the image data stored in the memory 73 of the digitalcopying machine 92. Also, the image data are transferred in the samemanner as directly sending the image data explained above. Accordingly,the digital copying machine 93 receives the transferred image data andstores the same in its own memory 73.

The digital copying machine 92 carries out S33-S40 repetitively untilthe entire document is read (S41). When the document reading ends, andin case that the external memory is used (S42), the digital copyingmachine 93 returns the image data to the digital copying machine 92 inthe output order, so that the digital copying machine 92 can steadilyoutput the returned image data in the form of an image on a sheet (S43).Herein, the output order is a descending order in page numbers.

The image data are retrieved from each memory 73 in the same manner asthe writing operation. To be more specific, the image data are retrievedfrom the memory 73 of the digital copying machine 92 through a data linewithin the digital copying machine 92, whereas the image data areretrieved from the memory 73 of the digital copying machine 93 throughthe transmission line 96.

On the other hand, if an available capacity of the memory 73 of thedigital copying machine 92 is sufficient to store the image data of therest of the document in S35, the digital copying machine 92 continues tostore the image data into its own memory 73 (S44), and proceeds to S41.Subsequently, the digital copying machine 92 carries out S41 and S42,and steadily outputs the image data stored in its own memory 73 onto asheet in an output order (S46).

When a predetermined time limit has passed before the operator pressesthe external memory selection key 121a in S38 (S45), the digital copyingmachine 92 proceeds to S42 and steadily outputs the image data stored inits own memory 73 up to that point onto a sheet in an output order(S46).

In the above explanation, the digital copying machine 92 is arranged tostore the image data into its own memory 73 to its full capacity;however, some pages of which may be secured as an operation area usedexclusively for its control operation.

Further, the present image forming system is arranged in such a mannerthat, when the digital copying machine 93 receives a job request of anedit function which is not provided therein, or a store request in avolume exceeding an available capacity of its memory 73 from any otherdigital copying machine, a message that the digital copying machine 93can not accept the job request will be displayed on the liquid crystaldisplay device 1 of the digital copying machine that has sent the jobrequest. In short, every time the digital copying machine 93 receives ajob request, it checks the content of the same by means of the PCU 74.

When the digital copying machine 93 can carry out the requested job, itdoes so simply; otherwise, the digital copying machine 93 transmits dataindicating that it can not carry out the requested job to therequest-sender digital copying machine. Upon receipt of such data, therequest-sender digital copying machine displays a corresponding messageon its liquid crystal display device 1.

Described in the following is a method of deleting the storage contentwhich have been stored in the memory 73, serving as the storage means ofthe digital copying machine 93, at the request from and on behalf of thedigital copying machine 92, serving as the first image formingapparatus.

The present image forming system is arranged in such a manner that ifthe digital copying machine 93 does not receive a return request fromthe digital copying machine 92 within a predetermined period, thedigital copying machine 93 automatically erases the image data andappended data which have been stored in its own memory 73 on behalf ofthe digital copying machine 92 at its request to reduce the capacitiveburden of the memory 73.

In other words, the present image forming system is arranged in such amanner that the digital copying machine 93 erases the image data if ithas not received the return request from the request-sender digitalcopying machine (herein machine 92) for a considerable period, therebypreventing its own memory 73 from accumulating the image dataunnecessarily. This arrangement makes it possible to prevent the memory73 being occupied unnecessary to reduce the burden in a copyingoperation of its own digital copying machine 93.

The above image data erasing operation will be explained with referenceto the flowchart of FIG. 1.

Assume again that the digital copying machine 92 needs the memory 73 ofthe digital copying machine 93 as the external memory to carry out thejob.

As previously explained, the digital copying machine 92 includes the64M-byte page memory as the memory 73, into which 256-level image dataof up to four Japanese Standard A4 size papers can be stored.

A 64M-byte memory is sufficient for an ordinary copying operation wherea copy of the document is made after the image data thereof are stored.However, in case that the operator wishes to make several copies of a10-page document using the electronic RDH function, the image data of 6pages exceeds the capacity of the memory 73.

Herein, the image data being read are steadily accumulated in the memory73 of the digital copying machine 92 to its full, and when the memory 73becomes full, a message is displayed on the screen as shown in FIG.17(a) to so inform the operator.

The operator determines whether he wishes to use the external memory ornot, and if he wishes so, he presses the external memory key 121a toinput an external memory job command. Accordingly, the screen of theliquid crystal display device 1 switches to the one with a message asshown in FIG. 17(b).

As soon as the operator presses the continue key 121c in the switchedscreen, the screen again switches to the one as shown in FIG. 17(c) toindicate that the digital copying machine 92 is now carrying out the jobusing the external memory.

Also, as soon as the operator presses the continue key 121c, the digitalcopying machine 92 starts to transfer the image data of the document tothe digital copying machine 93 through the transmitting apparatus.

As is detailed by the flowchart in FIG. 1, the digital copying machine93 receives the transferred image data of the document (S51), andsteadily stores the same into its own memory 73 (S52).

Consequently, the image data of six pages of the document aretemporarily stored in the memory 73 of the digital copying machine 93.Note that the memory 73 is managed in the environments that disallow anydata loss. To be more specific, the above memory 73 is composed of anon-volatile memory, such as a memory with a back-up power source and aflash memory, so that it does not lose the image data once they arestored therein, should a power supply to the main body of the digitalcopying machine 93 accidentally stop.

When the document reading ends, the digital copying machine 92 retrievesthe image data stored in its own memory 73 to output the same to producea printed record through the laser printer section 32 in a descendingorder in page numbers, after which the digital copying machine 92 sendsa return request to the digital copying machine 93 (S54). Upon receiptof the return request, the digital copying machine 93 retrieves theimage data from its own memory 73 and returns the same to the digitalcopying machine 92 (S55). Then, the digital copying machine 92 outputsthe returned image data and produce a printed record in the same manneras above. More specifically, the image data retrieved from the memory 73of the digital copying machine 93 are sent through the transmittingapparatus within the image forming system in the same manner as theimage data writing operation. In short, the image data are steadilyretrieved per page and returned to the digital copying machine 92 toproduce a printed record of the same.

The digital copying machine 93 sets a timer serving as time measuringmeans when its own memory 73 started to store the image data from thedigital copying machine 92 in S52 to manage a time interval (S53). Whena predetermined time has passed (S56), the digital copying machine 93erases the image data stored in its own memory 73 on behalf of thedigital copying machine 92 (S57). This arrangement prevents the memory73 of the digital copying machine 93 from storing the same image datafor a considerable period.

The time interval can be set arbitrary depending on the structure of theimage forming system. For example, if the image forming system compriseshigh-speed digital copying machines, the time interval can be short. Onthe other hand, if the image forming system comprises low-speed digitalcopying machines, the time interval may be longer. This arrangementdisallows the memory 73 to erase valid image data together with invalidimage data.

As has been explained, the present image forming system is arranged insuch a manner that when the memory 73 of the digital copying machine 92is insufficient to carry out the electronic RDH function, the operatorcan input a command to send a job request to the digital copying machine93 to use its memory 73 by manipulating the control panel 90 serving ascommand input means. When the operator inputs a command to issue the jobrequest to use the memory 73 of the digital copying machine 93 throughthe control panel 90 of the digital copying machine 92, the PCU 74 ofthe digital copying machine 92 transfers the image data that have beenstored in its own memory 73 to the digital copying machine 93 at the jobrequest. The image data are transferred either partially or entirely.

Upon receipt of the image data through the transmitting apparatus, thedigital copying machine 93 stores the same into its own memory 73serving as the storage means. The digital copying machine 93 waits for areturn request from the digital copying machine 92, and upon receipt ofthe same, it returns the image data to the digital copying machine 92through the transmitting apparatus.

Accordingly, the digital copying machine 92 stores the returned imagedata into its own memory 73 first, and thence retrieves the stored imagedata and inputs the same into the laser printer section 32.Consequently, the digital copying machine 92 outputs the input imagedata to produce a printed record in the form of a visible image by meansof the laser printer section 32 under the control of the PCU 74.

According to the above arrangement, the operator can carry out a jobthat demands a memory of a great capacity even when the digital copyingmachine 92 he is manipulating has the memory 73 with an insufficientcapacity, because the digital copying machine 92 can use the memory 73of the digital copying machine 93.

On the other hand, the PCU 74 of the digital copying machine 93 servingas erasing means erases the image data in its own memory 73 if no returnrequest is sent from the digital copying machine 92 within apredetermined time interval measured by the timer.

In other words, when the digital copying machine 92, which has issued ajob request to the digital copying machine 93 to store the image data onits behalf, has not had any contact for a considerable period, the imagedata stored in the memory 73 of the digital copying machine 93 areerased to reduce the burden thereof, thereby making it possible toutilize the memory 73 of the digital copying machine 93 to its fullcapacity. In other words, the digital copying machine 93 is arranged notonly to accumulate the image data on behalf of any other digital copyingmachine at its request, but also to erase the image data thusaccumulated when the accumulated image data become a considerable burdenon its operation after judging the validity thereof. This arrangementmakes it possible to prevent the memory 73 from being occupied byinvalid image data for a considerable period to reduce the burden of thedigital copying machine 93 in its own copying operation. Consequently,the present image forming system as a whole can always handle a greatvolume of image data efficiently in an optimal condition.

Since the time interval can be set arbitrary in the timer, invalid imagedata are erased based on an adequate time interval in the entire imageforming system, whether the image forming system is composed ofhigh-speed or low-speed machines. In other words, a long time intervalis given to the low-speed machines, so that the request-receivingdigital copying machine will not erase the transmitted image datawithout giving an ample time for a low-speed request-sending digitalcopying machine to issue a return request.

Since the above memory 73 of the digital copying machine 93, where theimage data from the digital copying machine 92 are stored temporarily,is composed of a non-volatile memory, such as a memory with a back-uppower source and a flash memory, it does not lose the image data, shoulda main power supply to the digital copying machine main bodyaccidentally stop. This arrangement ensures the memory 73 of the digitalcopying machine 93 not to lose the image data transferred from any othercopying machine with a store request, thereby eliminating unwanted jobto ask the request-sender copying machines to send the job request againdue to accidental data loss.

(Embodiment 2)

Referring to FIGS. 18 and 19, the following description will describeanother example embodiment of the present invention. Hereinafter, likecomponents are labeled with like reference numerals with respect to theEmbodiment 1, and the description of these components is not repeatedfor the explanation's convenience.

In the image forming system of Embodiment 1, the image data areautomatically erased from the memory 73 when the predetermined time haspassed in S56 of the flowchart of FIG. 1 (S57). However, this may bemodified. For example, before the image data are erased from the memory73, the operating condition of the machine that has sent the storerequest, namely the digital copying machine 92 herein, may be checkedwhen the predetermined time has passed. Then, whether the image datashould be erased or not is determined based on the confirmed operatingconditions.

For example, as shown in FIG. 18, after the digital copying machine 93receives the image data and appended data, such as its machine ID(identification) No., from the digital copying machine 92 (S61), thedigital copying machine 93 stores the received image data and appendeddata into its memory 73 (S62). Also, the image digital copying machine93 sets a timer when the image data and appended data are started beingstored (S63). Assume a timer is set for 10 minutes herein.

Subsequently, the digital copying machine 93 waits for a return requestfrom the digital copying machine 92 (S64), and upon receipt of thereturn request, returns the image data to the digital copying machine 92(S65), after which the digital copying machine 92 resets the timer(S66).

On the other hand, if there is no return request from the digitalcopying machine 92 in S64, whether the predetermine time, 10 minutes,has passed or not is checked (S67). When 10 minuets have passed, thedigital copying machine 93 resets the timer (S68), and confirms theoperating condition of the request-sender digital copying machine 92through the transmitting apparatus (S69).

Next, if the request-sender digital copying machine 92 is in operation(S70), the digital copying machine 93 sets the timer again (S71) becausethe digital copying machine 92 may send the return request after it endsthe current operation. Then, the digital copying machine 93 returns toS64 and waits for the return request again. As previously mentioned, thetime interval set for the timer in S71 is determined based on theperformance level of each digital copying machine within the imageforming system. As the time interval is set for 10 minutes in S63, thetime interval is set, for example, 5 minutes, in S71.

If the digital copying machine 92 is not in operation in S70, thedigital copying machine 93 erases the image data stored in its ownmemory 73 on behalf of the digital copying machine 92 (S72).

Further, if the time has not been up yet in S67, the digital copyingmachine 93 returns to S64 and waits for the return request.

In the present image forming system, the image data in the memory 73 areautomatically erased in S70 and S72. However, as shown in FIG. 19, itcan be modified in such a manner that the operator can manually erasethe image data. To be more specific, the liquid crystal display device 1on the control panel 90 of the digital copying machine 93 may bearranged to display the operating condition of the request-senderdigital copying machine 92, so that the operator can confirm theoperating condition of the digital copying machine 92 and erase theimage data manually using the display.

As shown in the drawing, the screen displays a table, which contains:"No." indicating serial numbers of the requests; "request condition"indicating the content of the store request, namely, the size andquantity of the document; "request-sender machine" identifying thedigital copying machine that has sent the store request; "operatingcondition" indicating whether the request-sender machine is in operationor a ready state; and "time lapse" indicating a lapse of time since thetransferred image data are stored in the memory 73.

In addition, the state and available capacity of the memory 73 aredisplayed below the above display areas, so that the operator canconfirm the availability of the same. Further, an up key 130a and a downkey 130b are displayed at the right side of the screen to enable theoperator to move a cursor displayed in the left side of the tablevertically. Thus, the operator moves the cursor next to the serial No.of the image data he wishes to erase and presses a clear key 132. Then,the corresponding image data are erased from the memory 73.

According to the above arrangement, the operator can check the operatingcondition of the request-sender digital copying machine 92. Thus, if therequest-sender digital copying machine 92 is in a ready state, the sameis judged to have finished the copying job for the image data of adocument in question. Also, if the power supply to the request-senderdigital copying machine 92 is turned off, the same is practically reset.Thus, the digital copying machine 93 can erase the image data stored inits own memory 73 under these conditions, either automatically or by theoperator's manual operation.

As has been explained, in the present image forming system, the digitalcopying machine 93 does not return the image data to the digital copyingmachine 92 unless the return request is received. Thus, if the operatingcondition of the digital copying machine 92 were undetectable, thedigital copying machine 93 could not erase the image data from itsmemory 73 even when the return request has not been received for aconsiderable period and storing such image data is becoming a burden forits operation.

Therefore, to eliminate this problem, the PCU 74 of the digital copyingmachine 93 serves as condition confirming means for confirming theoperating conditions of the digital copying machine 92, such as "inoperation", "ready", "power off", etc. Consequently, the digital copyingmachine 93 can confirm the operating condition of the digital copyingmachine 92 through signal transmission by means of the PCU 74.

For example, in case of "in operation", the digital copying machine 92is highly likely to issue the return request in the meantime, and incase of "ready" or "power off" when the return request has not beenissued yet, the stored image data in question can be judged as beinginvalid.

Thus, if the digital copying machine 93 has not received the returnrequest for a considerable period, it confirms the operating conditionof the digital copying machine 92.

To reduce the capacitive burden of the memory 73 of the digital copyingmachine 93, the digital copying machine 93 can automatically erase thestored image data upon confirming "ready" or "power off" state.

Conversely, it has become possible to prevent the erroneous erasing ofthe image data that should be stored by confirming the operatingcondition of the digital copying machine 92 before erasing the imagedata stored in the memory 73 of the digital copying machine 93 on itsbehalf.

In the present image forming system, the PCU 74 of the digital copyingmachine 93 serving as the condition confirming means confirms theoperating condition of the digital copying machine 92 in the abovemanner and displays the same in messages, "IN OPERATION", "READY", or"POWER OFF", on the liquid crystal display device 1 which also serves asthe condition confirming means.

This arrangement enables the operator using the digital copying machine93 to erase the image data in its own memory 73 by confirming theoperating condition of the digital copying machine 92 displayed on thescreen.

Also, in the present image forming system, the image data from thedigital copying machine 92 are stored temporarily in the memory 73 ofthe digital copying machine 93 with appended data, such as a machine IDNo. of the request-sender machine. Further, it can be modified in such amanner that appended data are displayed on the liquid crystal displaydevice 1 serving as a display device together with the operatingcondition.

The above arrangement makes it possible to confirm which digital copyingmachine has issued which store request when more than one store requestis issued. Thus, before erasing the image data that have been left for aconsiderable period or seem invalid, the digital copying machine 93identifies the request-sender digital copying machine of such image databased on the machine ID No.

The machine ID No. is used as the appended data of the image dataherein; however, data related to the time when the image data aretransferred to the digital copying machine 93 from the digital copyingmachine 92 may be used as the appended data. In this case, for how longthe image data are stored in the memory 73 of the digital copyingmachine 93 can be confirmed more accurately.

In addition, when the memory 73 of the digital copying machine 93 storesthe image data on behalf of more than one first image forming apparatus,it is arranged in such a manner that the image data can be erasedseparately for each first image forming apparatus.

Thus, of all the image data stored on behalf of the first image formingapparatuses, only the invalid image data can be erased selectively fromthe memory 73 of the digital copying machine 93.

(Embodiment 3)

Referring to FIG. 20, the following description will describe a furtherexample embodiment of the present invention. Hereinafter, likecomponents are labeled with like reference numerals with respect to theEmbodiments 1 and 2, and the description of these components is notrepeated for the explanation's convenience.

Assuming that the same request-sender digital copying machine issuesanother store request, then how the digital copying machine 93 handlesthe image data stored in the memory 73 at the preceding store requestwill be explained.

To be more specific, the digital copying machine 93 erases the imagedata stored in its own memory 73 at the preceding store request uponreceipt of another store request from the same digital copying machine,so that only the invalid image data are erased in a reliable manner.

If the appended data are used to identify the request-sender digitalcopying machine for each store request as previously mentioned, it canbe readily confirmed whether both the current and preceding storerequests were issued by the same digital copying machine or not.

However, it is important to judge whether a group of the image datatransferred at regular time intervals should be processed as a singledocument, or separate documents. Because even when the image data of thedocument are transferred per page, the image data for each page are notnecessarily transferred at regular intervals, in other words, theintervals can vary.

Thus, a predetermined level is set to a minimum time interval guaranteedby each apparatus in the image forming system according to its operationlevel, and the image data transferred within this predetermined time arestored in the memory 73 as those of a single document whether they aretransferred at regular or irregular intervals. On the other hand, evenwhen a group of the image data are transferred from the same digitalcopying machine, the image data transferred after the predetermined timehas passed are stored in the memory 73 as those of a separate documentfrom the document transmitted within the predetermined time.

The above operation of the digital copying machine 93 is detailed by theflowchart of FIG. 20. For example, upon receipt of the image data andappended data from the digital copying machine 92 (S81), the digitalcopying machine 93 stores the same into its memory 73 together with thedata indicating a receipt time (S82). Then, the digital copying machine93 checks whether the latest image data are transferred from the samedigital copying machine (herein machine 92) that has issued thepreceding store request (S83). If so, the lapse time is checked (S84) todetermine whether the latest image data are transferred within thepredetermined time since the second latest image data were transferredat the preceding store request (S85). If the latest image data aretransferred within the predetermined time, the digital copying machine93 does not take any action; otherwise, the digital copying machine 93erases the other image data accumulated in the memory 73 prior to thelatest image data (S86).

The present image forming system is arranged in such a manner that thedigital copying machine 93 stores the image data temporarily in itsmemory 73 on behalf of the digital copying machine 92, and returns thesame only after it has received the return request from the digitalcopying machine 92. However, there may be a case that the digitalcopying machine 93 has not received the return request for aconsiderable period.

Under these conditions, if the image data are transferred from thedigital copying machine 92 again, it is most likely that the digitalcopying machine 92 has already produced a printed record of the imagedata stored in the memory 73 of the digital copying machine 93, and isnow operating for another document. Thus, most of these cases, the imagedata stored in the memory 73 are no longer valid.

Therefore, the digital copying machine 93 judges that the image datathat have been stored at the preceding store request should be erased.

In the present embodiment, the PCU 74 of the digital copying machine 93serving as judging means confirms whether the latest image data are alsotransferred from the digital copying machine 92 that has issued thepreceding store request based on the appended data, such as the machineID No., every time the digital copying machine 93 receives a storerequest.

If the PCU 74 of the digital copying machine 93 confirms that the latestimage data are transferred from the digital copying machine 92 that hasissued the preceding store request, the digital copying machine 93erases the image data stored in its own memory 73 on behalf of thedigital copying machine 92 at its preceding store request under thecontrol of the PCU 74.

Consequently, the digital copying machine 93 can reduce the capacitiveburden of its memory 73 by erasing invalid image data.

However, note that the present image forming system is arranged in sucha manner that the digital copying machine 93 does not erase the imagedata stored in its memory 73 at the preceding store request from thedigital copying machine 92 unconditionally. The digital copying machine93 inhibits the erasing of the image data under certain conditions.

For example, it can be arranged that the digital copying machine 93 doesnot erase any image data in the memory 73 until a predetermined time haspassed.

Therefore, the digital copying machine 93 judges a group of the imagedata transferred within the predetermined time as being the image dataof a single document. For example, even when a group the image data ofseveral pages out of a 50-page document are transferred at random or theimage data of the first and twentieth pages of the document aretransferred separately at a moderate time interval, it has becomepossible to prevent the erroneous erasing of the image data by judgingthe group of the image data as belonging to separate documents.

(Embodiment 4)

Referring to FIG. 21, the following description will describe stillanother example embodiment of the present invention. Hereinafter, likecomponents are labeled with like reference numerals with respect toEmbodiments 1-3, and the description of these components is not repeatedfor the explanation's convenience.

A typical digital copying machine is provided with an auto-clearfunction that resets the copy quantity, copying mode, etc. to theinitial state after a predetermined time has passed since the copyingoperation ends. However, it is not desirable if the request-receiverdigital copying machine erases all the image data stored thereinincluding those stored on behalf of the request-sender digital copyingmachine each time the auto-clear function is effected.

To eliminate this problem, the image forming system of the presentembodiment is arranged in such a manner that the image data are noterased unless a predetermined time has passed even when all the otherfunctions of the request-receiver digital copying machine are reset bythe auto-clear function.

The above operation will be detailed with reference to the flowchart ofFIG. 21. To begin with, when the digital copying machine 93 ends thecopying operation (S90), the digital copying machine 93 sets its timer(S91). In the meantime, the digital copying machine 93 checks whetherthe time is up or not (S92), and if the time is up, the digital copyingmachine 93 resets itself to the standard mode by effecting theauto-clear function. Note that, however, the image data storing area inthe memory 73 is left intact at this point (S93). Next, the digitalcopying machine 93 resets the timer and returns to S91.

On the other hand, when the time is not up yet in S92 and the operatorhas manipulated keys (S95), whether the copying operation start key 15is pressed or not is checked (S96). If so, the digital copying machine93 resets the timer (S97), and carries out the copying operation (S98).If the start key 15 has not been pressed, the digital copying machine 93resets the timer (S99) and returns to S91.

Thus, in the image forming system of the present embodiment, the PCU 74of the digital copying machine 93 is provided to serve as reset meansfor erasing the image data in the memory 73 based on an auto-clear resetsignal, and also to serve as inhibiting means for inhibiting the erasingof the image data and appended data stored in the memory 73 on behalf ofany other digital copying machine (machine 92, herein) at its request.

In other words, a typical digital copying machine is arranged to resetitself to the initial state based on the auto-clear reset signal when apredetermined time has passed since the copying operation ends.

Naturally, the digital copying machine 93 of the present embodimentresets itself in response to the auto-clear signal and erases the imagedata in its own memory 73.

However, it is not desirable if the digital copying machine 93 erasesthe image data stored in its memory 73 on behalf of any other digitalcopying machine as well by effecting the auto-clear function.

To eliminate this problem, when the digital copying machine 93 resetsitself in response to the auto-clear reset signal, the PCU 74 inhibitsthe erasing of the image data and appended data stored in its memory 73on behalf of any other digital copying machine.

Consequently, it has become possible to inhibit the erroneous erasing ofthe image data temporarily stored in the memory 73 of the digitalcopying machine 93 on behalf of the digital copying machine 92.

(Embodiment 5)

Referring to FIGS. 22 and 23, the following description will describestill another example embodiment of the present invention. Hereinafter,like components are labeled with like reference numerals with respect toEmbodiments 1-4, and the description of these components is not repeatedfor the explanation's convenience.

As shown in FIG. 22, an image forming system of the present embodimentincludes six digital copying machines 201-206, which include interfaces201a-206a, respectively to enable mutual data transmission. The digitalcopying machine 201 having the largest memory and the digital copyingmachine 202 having the greatest number of image processing functionsconstitute a main digital copying machine, namely, the second imageforming apparatus.

The digital copying machines 201 serving as a first main digital copyingmachine and the digital copying machine 202 serving as a second maindigital copying machine are connected to each other through theirrespective interfaces 201a and 202a and the transmission line 96.Likewise, the digital copying machine 203-206 are connected individuallyto the digital copying machine 201 through their respective interfaces203a-206a, 201a, and the transmission lines 96. Hence, the digitalcopying machines 202-206 are interconnected through the digital copyingmachine 201 for mutual data transmission.

As previously mentioned, in the present image forming system, thedigital copying machines 201 and 202 constitute the main digital copyingmachine which carries out the operations explained in Embodiment 1above. For example, the digital copying machine 202 corresponds to thedigital copying machine 93 of FIG. 11, and the digital copying machine201 has a larger memory and fewer image processing functions than thedigital copying machine 93. Also, the digital copying machines 203 and204 correspond to the digital copying machine 92 in function and thedigital copying machines 205 and 206 correspond to the digital copyingmachine 91 in function.

In the main digital copying machine, the digital copying machine 201 isresponsible for managing the image data demanding the memory 73 with alarge capacity, while the digital copying machine 202 is responsible forthe image processing. To be more specific, when the digital copyingmachine 203 issues a job request of image processing, the image datasent from the digital copying machine 203 are stored in the memory 73 ofthe digital copying machine 201, and steadily sent therefrom to thedigital copying machine 202 to be processed.

The processed image data are stored in the memory 73 of the digitalcopying machine 201 again, and returned therefrom to the digital copyingmachine 203. The above operation is carried out under the control of,for example, the PCU 74 of the digital copying machine 201.

When the main digital copying machine is composed of a plurality ofdigital copying machines each taking their respective roles, not onlythe cost can be saved, but also the overall efficiency of the imageforming system can be improved compared with a case of purchasing asingle digital copying machine provided with high-grade functions.

Alternatively, the image forming system of the present embodiment may bemodified in the following manner.

As shown in FIG. 23, the alternative image forming system comprises fivedigital copying machines 211-215, which have their respectivetransmission interfaces 211a-215a. The digital copying machines 211-215are interconnected through the interfaces 211a-215a and the transmissionlines 96 to constitute a loop network. Each of the digital copyingmachines 211-215 is identical with the digital copying machine 30 instructure.

In the present image forming system, if any of the digital copyingmachines 211-215 the operator is manipulating does not have a desiredimage processing function, the manipulated digital copying machineissues a job request to the other digital copying machines to carry outthat particular function on its behalf. To realize above arrangement,each of the digital copying machines 211-215 withholds data as to theimage processing functions and memory capacities of the other digitalcopying machines. The job request can be issued either automatically ormanually. In case that the job request is issued manually, the digitalcopying machines that have the desired function are displayed on theliquid crystal display device 1, and the operator selects the digitalcopying machine from those displayed on the screen.

The present image forming system is arranged to operate in the samemanner as its counterpart in Embodiment 1. Here, it is not the maindigital copying machine that receives a job request from therequest-sender digital copying machine, but the digital copying machinehaving a specific image processing function the operator wishes to use.

The present image forming system, in which the main digital copyingmachine is not specified, is advantageous when each of the digitalcopying machines 211-215 has different image processing functions.

(Embodiment 6)

Referring to FIGS. 24-27, the following description will describe stillanother example embodiment of the present invention.

As shown in FIG. 24, an image forming system of the present embodimentincludes three digital copying machines 91-93, a scanner 94, and aprinter 95 serving as an image forming apparatus installed in an office,and a large-scale host computer 99 serving as an image processingapparatus installed in an external service center. The service centerprovides various kinds of data service including high-quality imageprocessing.

The scanner 94 and printer 95 are connected to the digital copyingmachine 93 through interfaces 94a and 95a, respectively, so that eachcan transmit data mutually with the digital copying machine 93. Notethat the image data transmission unit 81 of FIG. 4 corresponds to, forexample, the interface 93a alone, or both the interface 93a and a modem98 of the digital copying machine 93 of FIG. 24.

The host computer 99 includes a high-speed data processing CPU, ahigh-speed editing algorithm, a high-speed data recognizing algorithm, amemory with a capacity far larger than the memory 73, various kinds ofdatabases for recognizing paper money or the like, and an interface 99a.

The digital copying machine 93 and host computer 99 are connected toeach other through their respective interfaces 93a and 99a and atelephone line 97. Note that the telephone line 97 may be replaced withany other adequate transmission line 96, such as optical fibers. Twogeneral ISDN (Integrated Services Digital Network)-capable modems(modulator) 98 are provided to the digital copying machine 93 and hostcomputer 99, respectively. Each modem 98 converts a digitalized electricsignal into a signal which can be transmitted through the telephone line97. Each modem 98 adopts the PM (Phase Modulation) method, AM (AmplitudeModulation) method, FM (Frequency Modulation) method, or the like.Herein, the interfaces 91a-95a and 99a, transmission lines 96, telephoneline 97, two modems 98 constitute the transmitting apparatus. The kindsof data this device can handle are previously explained.

The digital copying machines 91-93 and host computer 99 can mutuallytransmit various kinds of data, such as control command codes and bitdata represented by image contrast data, through the telephone line 97.

A single office is connected to the service center in FIG. 24; however,a great number of users' offices throughout the nation are connected tothe service center in practice.

Also, the job of the host computer 99 is to provide high-quality imageprocessing functions including image edit functions and high-speed imageprocessing, and the host computer 99 includes at least the functionsprovided to an ordinary digital copying machine. However, the hostcomputer may omit too basic functions provided to an inexpensive model.In short, the host computer 99 includes only the adequate functions theservice center is expect to provide.

Incidentally, new image processing functions have been steadilydeveloped in accordance with the demand of constructing infrastructureor improvement in work efficiency. Thus, new processing functions can beadded to the host computer 99, or replace with the processing functionsused less frequently.

Here, example image edit functions provided to the digital copyingmachines 91-93 and host computer 99 are tabulated for ready comparisonin Table 3 below.

                  TABLE 3                                                         ______________________________________                                        IMAGE            MA-     MA-     MA-   COM-                                   EDIT             CHINE   CHINE   CHINE PUTER                                  FUNCTION         91      92      93    99                                     ______________________________________                                        INDEPENDENT SCALING                                                                            ∘                                                                         ∘                                                                         ∘                                                                       ∘                          SHARPNESS                ∘                                                                         ∘                                                                       ∘                          BINDING MARGIN   ∘                                                                         ∘                                                                         ∘                                                                       ∘                          FRAME ELIMINATION                                                                              ∘                                                                         ∘                                                                         ∘                                                                       ∘                          CENTERING                ∘                                                                         ∘                                                                       ∘                          1-SET-2-COPY             ∘                                                                         ∘                                                                       ∘                          ADDRESSED COPY                   ∘                                                                       ∘                          MULTI-SHOT               ∘                                                                         ∘                                                                       ∘                          TRIMMING · MASKING                                                                            ∘                                                                         ∘                                                                       ∘                          MOVE                     ∘                                                                         ∘                                                                       ∘                          SYNTHESIS FUNCTION               ∘                                                                       ∘                          MONOCHROMIC INVERSE                                                                            ∘                                                                         ∘                                                                         ∘                                                                       ∘                          CROSSHATCH/SHADE                                                              SHADOW · OUTLINE        ∘                                                                       ∘                          ITALIC · MIRROR IMAGE   ∘                                                                       ∘                          REPEAT COPY      ∘                                                                         ∘                                                                         ∘                                                                       ∘                          2-IN-1-COPY                      ∘                                                                       ∘                          DATED COPY · CENTER MARK                                                                              ∘                                                                       ∘                          ENLARGE/DIVIDE OUTPUT                  ∘                          TRANSLATION                            ∘                          HIGH-QUALITY PROCESSING                ∘                          ______________________________________                                    

Data related to these functions are stored in the memory 73 of eachdigital copying machines 91-93, and the PCU 74 of each machine refersthese data when necessary.

The present image forming system of FIG. 24 is arranged in the samemanner as its counterpart of FIG. 11. To be more specific, the digitalcopying machine 93 having the greatest number of image processingfunctions and largest memory 73 serves as the main digital copyingmachine, and the other digital copying machines 91 and 92, scanner 94and printer 95 are connected to the same.

In case that the operator selects the sharpness function when he ismanipulating the digital copying machine 91, the job is carried out aswas detailed by the flowchart of FIG. 15. Likewise, in case the memory73 of the digital copying machine 93 is shared by any other imagedigital copying machine, the job is carried out as was detailed by theflowchart of FIG. 16.

Next, the description will be given as to how the digital copyingmachine 93, serving as the request-receiver second image formingapparatus, erases the image data stored in its own memory 73 at therequest from and on behalf of the digital copying machine 92, serving asthe request-sender first image forming apparatus.

Like the aforementioned counterparts, the present image forming systemis arranged in such a manner that the digital copying machine 93 erasesthe image data and appended data stored in its own memory 73 at therequest from and on behalf of the digital copying machine 92 to reducethe capacitive burden of the memory 73 when the digital copying machine93 has not received a return request from the digital copying machine 92for a considerable period. However, unlike the above counterparts, thisoperation is carried out based on transfer history data made in recordsince the store request was received.

The transfer history data are stored in the form of a managing table ata storage area secured for its exclusive use in the memory 73 of thedigital copying machine 93, and displayed on the liquid crystal displaydevice 1.

To be more specific, as shown in FIG. 25, the screen displays a tablecontaining: "No." indicating serial numbers of the requests; "sheet"indicating the size of the document in question; "quantity" indicatingthe quantity of the document in question; "request-sender machine"identifying the digital copying machine that has sent the store requestto store the image data on its behalf; "receipt time" indicating thetime at which the transferred image data are stored in the memory 73;"return time" indicating the time at which the image data are returned;and "times" indicating how many times the image data are returned to therequest-sender digital copying machine.

In the above example, only one return time is displayed in the "returntime" column; however, all the return times may be displayed when theimage data have been returned more than once. This arrangement not onlymakes it possible to learn the image data return cycle, but alsofacilitates the management using other data, which will be describedbelow.

Of all the above display contents, "receive time", "latest return time","cycle", and "times" make up the transfer history data. However, thetransfer history data are not limited to these contents, and other kindsof data can be contained as well. Each content of the data can bedisplayed by scrolling the display screen.

Also, the current state of the memory 73 are indicated in an availablememory indicating portion 131 in the bottom of the display of FIG. 25 toenable the operator to confirm the current condition and availablecapacity of the memory 73. An up key 132a and a down key 132b areprovided in the right side of the display screen. A cursor 133 displayedat the left side of the table can be moved vertically by pressing the upkey 132a and down key 132b. To erase the respective image data from thememory 73, the operator selects the desired image data by moving thecursor 133 next to the corresponding serial No. and presses a clear key134.

Managing the return conditions of the stored image data as the transferhistory data makes it possible to erase the respective image data in thememory 73 either automatically or manually.

Next, a case where the digital copying machine 93 erases the image databased on the "times" in the transfer history data will be explained withreference to the flowchart of FIG. 26. Assume that the digital copyingmachine 93 shares its own memory 73 with the digital copying machine 93herein.

To begin with, the digital coping machine 93 checks whether the operatorhas pressed the copying switch, namely, the start key 15, (S101). If theoperator has pressed the start key 15, the digital copying machinecarries out the copying operation (S102), and in the meantime, checkswhether a specified quantity of copies are made to end the operation(S103).

When the operator has not pressed the start key 15 yet in S101, thedigital copying machine 93 checks whether it has received a storerequest (S104). When the digital copying machine 93 has received thestore request, it carries out memory processing (S105), which will bedetailed below (S105).

When the digital copying machine 93 has not received any store requestin S104, the digital copying machine 93 checks whether it has receivedany return request from the digital copying machine 92 (S106). Uponreceipt of the return request, the digital copying machine 93 retrievesthe image data from its own memory 73 and returns the same to thedigital copying machine 92 (S107), and after which the digital copyingmachine 93 increases the return image data managing counter by one(S108).

On the other hand, in case of no return request in S106, the digitalcopying machine 93 returns to S101.

The above memory processing in S105 will be detailed with reference tothe flowchart of FIG. 27.

Upon receipt of the store request, the digital copying machine 93 checksthe data size (volume) (S111), and judges whether its own memory 73 canstore the same or not by comparing the checked data volume with theavailable capacity of the memory 73 (S112).

When the memory 73 can store the image data, the digital copying machine93 so informs the digital copying machine 92 (S113), and receives theimage data from the digital copying machine 92 to store and manage thesame (S114).

When the memory 73 can not store the image data, the digital copyingmachine 93 checks whether any stored image data can be erased or notbased on the transfer history data (S115).

To be more specific, the PCU 74 of the digital copying machine 93 checksthe "times" in the transfer history data. When the "times" shows 0, thePCU 74 judges that the image data have never been returned, andtherefore, the image data can not be erased. When the "times" shows 1,the PCU 74 judges that the image data are returned to the digitalcopying machine 92 once and have less likelihood of receiving a returnrequest again. Thus, PCU 74 judges that the image data in question canbe erased. When the "times" shows 2 or greater, the PCU 74 judges thatthe digital copying machine 92 is set in a mode that demands the imagedata repetitively. Thus, it is preferable that the PCU 74 judges thatthe image data can not be erased.

When there are any erasable image data according to the above judgment(S116), the PCU 74 of the digital copying machine 93 erases thecorresponding image data from the memory 73 (S117).

On the other hand, when no image data are judged as being erasable inS116, the digital copying machine 93 informs the digital copying machine92 that it cannot accept the store request (S118).

In S116, the judgment is made based on the "times" in the transferhistory data; however, the same can be done based on the "return time".In other words, the same can be done based on the lapse time since theimage data were returned last time.

To be more specific, if the digital copying machine 93 has not receivedanother return request within a predetermined time since the image datawere returned at the last return request, the digital copying machine 93judges that no more return request will be issued for the image data inquestion, and therefore, the same can be erased.

However, the above predetermined time varies depending on theperformance level of each digital copying machine within the imageforming system. Thus, the present image forming system is arranged insuch a manner that the above predetermined time can be set arbitrary foreach digital copying machine based on its performance level.

Alternatively, the "return time" may be used in the following manner.That is, as shown in FIG. 25, the return time is recorded each time theimage data are returned, and a return request cycle is computed based onthe recorded data. If no return request is issued within the cycle thuscomputed since the last return request, it is least likely that anotherreturn request will be issued. Thus, the digital copying machine 93judges that the image data in question can be erased. In the example ofFIG. 25, the last five return requests were issued in every one minute,but the latest return request has not been issued more than one minutelater since the fifth return request was issued. Thus, if no returnrequest is issued within the time predetermined based on the returnrequest cycle, the corresponding image data are judged as beingerasable.

Further, the digital copying machine 93 can always communicate with therequest-sender digital copying machine 92 through the transmittingapparatus. Thus, the digital copying machine 93 may be arranged to erasethe image data from its memory 73 only when a deterministic condition issatisfied. Example deterministic conditions are: "the digital copyingmachine 92 has returned a signal acknowledging the receipt of the imagedata" or "the digital copying machine 92 has outputted the image dataand produced a printed record" after the image data were returned.

As has been explained, in the present image forming system, the PCU 74of the digital copying machine 93 serves as transfer history datamanaging means for managing the transfer history data of the image datasince the same were stored in its own memory 73, such as the number oftimes the image date were returned, the lapse time since the image datawere returned for the last time, and the cycle of returning the imagedata.

Thus, if the digital copying machine 93 has not received any returnrequest from the digital copying machine 92 for a considerable period,the digital copying machine 93 can check the transfer history data ofthe image data in question since the same were stored in its own memory73, and erase the same to reduce the capacitive burden of the memory 73.

When the "times" in the transfer history data is adopted, not only theactual number of times the image data returned at request can beconfirmed, but also the priority of the erasable image data can bedetermined.

To be more specific, when the "times" shows 0, the corresponding imagedata are placed at a lower rank, and when the "times" shows 2 orgreater, the corresponding image data are placed at a higher rank. In sodoing, the image data can be erased in a more accurate manner.

When the "lapse time" in the transfer history data is adopted, only theinvalid image data can be erased in a reliable manner.

Moreover, as has been explained, the predetermined time can be setarbitrary for each digital copying machine within the image formingsystem depending on their respective performance levels.

This arrangement eliminates the problem causing when each digitalcopying machine issues a return request at different time intervalswithin the image forming system.

Further, when the "cycle" in the transfer history data is adopted, itcan be predicted that no more return request will be issued for theparticular image data if a return request has not issued within thepredetermined cycle since the last return request was issued. Thus, theimage data can be erased in a more accurate manner.

Also, in the present image forming system, the PCU 74 of the digitalcopying machine 93 serves as erasing means, which distinguishes theerasable image data based on the transfer history data and erases thedistinguished image data in its memory 73.

Thus, when the digital copying machine 93 stores the image data in itsown memory 73 on behalf of the request-sender digital copying machine(herein, machine 92) for a considerable period, the digital copyingmachine 93 erases such image data to reduce the capacitive burden of itsmemory 73 and utilize the same efficiently.

Further, when the digital copying machine 93 stores the image data inits own memory 73 on behalf of more than one digital copying machine,the digital copying machine 93 can erase respective image dataselectively for a specific request-sender digital copying machine.

According to this arrangement, the digital copying machine 93 does noterase the image data stored in its memory 73 entirely; it erases onlythe image data that are no longer valid. Consequently, it has becomepossible to erase the image data in minimum volume, while leaving theimage data that should be stored in the memory 73 intact.

In the present image forming system, before the image data are erasedfrom the memory 73 of the digital copying machine 93, the PCU 74 of thesame serving as available capacity detecting means judges whether theavailable capacity of the memory 73 is sufficient to store the imagedata transmitted with the store request. The digital copying machine 93erases the image data only when the available capacity of its memory 73is not sufficient to store the transmitted image data.

Thus, the digital copying machine 93 can withhold the image data in itsown memory 73 on behalf of any other digital copying machine until theimage data are stored up to its full while securing a storage area usedexclusively for a particular function.

As a consequence, the digital copying machine 93 can secure a storagecapacity in its memory 73 necessary for its own operation, while at thesame time, withholding the image data, such as those to which a returnrequest may be issued repetitively, in its memory 73 to its full. Thisarrangement can prevent the erroneous erasing of the valid image data.

In the present image forming system, the digital copying machine 93 canconfirm whether it has received a signal acknowledging the receipt ofthe returned image data, or a signal informing producing a printedrecord of the returned image data from the digital copying machine 92before it erases the image data from its own memory 73.

This arrangement enables the digital copying machine 93 to accuratelydistinguish the erasable image data from the image data that should beleft intact, thereby inhibiting the storage of invalid image data in thememory 73 in a reliable manner.

As has been explained, the present image forming system is characterizedin that:

the second image forming apparatus includes the available capacitydetecting means for detecting an available capacity of the storagemeans; and

the erasing means starts to erase the image data from the storage meansbased on the transfer history data stored in the transfer history datamanaging means when the available capacity detecting means judges thatthe available capacity is not sufficient to store the transmitted imagedata with a store request.

According to this arrangement, the second image forming apparatus canstore the image data on behalf of the first image forming apparatus(es),while securing a storage capacity necessary for its own operation. Inother words, it has become possible to store the image data to which areturn request may be issued again as long as possible after the samewere returned at the last return request, thereby preventing theerroneous erasing of the same.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. An image forming system comprising a first imageforming apparatus, a second image forming apparatus, and a transmittingapparatus for connecting said first and second image forming apparatusesfor mutual image data transmission, wherein,(1) said first image formingapparatus includes:a recording section for forming a visible image basedon image data; a command input section for inputting an action command;and a control section for transferring said image data from said firstimage forming apparatus to said second image forming apparatus throughsaid transmitting apparatus at a command, inputted through said commandinput section, to issue a store request to said second image formingapparatus to store said image data on behalf of said first image formingapparatus, and (2) said second image forming apparatus includes:astorage section for storing image data; a control section for storingsaid transferred image data from said first image forming apparatus intosaid storage section, and for returning said stored image data to saidfirst image forming apparatus through said transmitting apparatus at areturn request issued by said first image forming apparatus; a timemeasuring section for measuring a predetermined period since saidtransferred image data are stored in said storage section; and anerasing section for erasing only said stored image data and informationrelated to said stored image data in said storage section when saidfirst image forming apparatus has issued no return request within saidpredetermined period.
 2. The image forming system as defined in claim 1,wherein said second image forming apparatus further includes:a resetsection for erasing a content of said storage section in response to areset signal; an inhibiting section for inhibiting said reset sectionfrom erasing said stored image data in said storage section.
 3. An imageforming system comprising a first image forming apparatus, a secondimage forming apparatus, and a transmitting apparatus for connectingsaid first and second image forming apparatuses for mutual image datatransmission, wherein,(1) said first image forming apparatus includes arecording section for forming a visible image based on image data;acommand input section for inputting an action command: and a controlsection for transferring said image data from said first image formingapparatus to said second image forming apparatus through saidtransmitting apparatus at a command, inputted through said command inputsection, to issue a store request to said second image forming apparatusto store said image data on behalf of said first image formingapparatus, and (2) said second image forming apparatus includes:astorage section for storing image data; an erasing section for erasingonly said stored image data and information related to said stored imagedata in said storage section; a condition confirming section forconfirming an operating condition of said first image forming apparatus;and a control section for storing said transferred image data from saidfirst image forming apparatus into said storage section, and forperforming, based on a return request issued by said first image formingapparatus, the operations of returning said stored image data to saidfirst image forming apparatus through said transmitting apparatus, andcontrolling erasing operations of said erasing section based on theoperating condition of said first image forming apparatus confirmed bysaid condition confirming section; wherein said second image formingapparatus further includes a time measuring section for measuring apredetermined period since said transferred image data are stored insaid storage section, whereby said condition confirming section confirmsthe operating condition of said first image forming apparatus when saidfirst image forming apparatus has issued no return request within saidpredetermined period.
 4. An image forming system comprising a firstimage forming apparatus, a second image forming apparatus, and atransmitting apparatus for connecting said first and second imageforming apparatuses for mutual image data transmission, wherein,(1) saidfirst image forming apparatus includes a recording section for forming avisible image based on image data;a command input section for inputtingan action command: and a control section for transferring said imagedata from said first image forming apparatus to said second imageforming apparatus through said transmitting apparatus at a command,inputted through said command input section, to issue a store request tosaid second image forming apparatus to store said image data on behalfof said first image forming apparatus, and (2) said second image formingapparatus includes:a storage section for storing image data; an erasingsection for erasing only said stored image data and information relatedto said stored image data in said storage section; a conditionconfirming section for confirming an operating condition of said firstimage forming apparatus; and a control section for storing saidtransferred image data from said first image forming apparatus into saidstorage section, and for performing, based on a return request issued bysaid first image forming apparatus, the operations of returning saidstored image data to said first image forming apparatus through saidtransmitting apparatus, and controlling erasing operations of saiderasing section based on the operating condition of said first imageforming apparatus confirmed by said condition confirming section;wherein said condition confirming section confirms whether said firstimage forming apparatus is operating or not, whereby said erasingsection erases said stored image data when said condition confirmingsection confirms that said first image forming apparatus is notoperating.
 5. An image forming system comprising a plurality of firstimage forming apparatuses, at least one second image forming apparatus,and a transmitting apparatus for connecting said first and second imageforming apparatuses for mutual image data transmission, wherein,(1) saideach first image forming apparatus includes:recording section forforming a visible image based on image data; a command input section forinputting an action command; and a control section for transferring saidimage data from its own first image forming apparatus to said secondimage forming apparatus through said transmitting apparatus togetherwith appended data at a command to issue a store request to said secondimage forming apparatus to store said image data on behalf of its ownfirst image forming apparatus, said command being inputted through saidcommand input section, said appended data being data identifying its ownfirst image forming apparatus as a request sender, and (2) said secondimage forming apparatus includes:a storage section for storing imagedata; a control section for storing said transferred image data andappended data from said first image forming apparatus into said storagesection, and for returning said stored image data to the first imageforming apparatus that has issued said store request through saidapparatus transmitting apparatus at a return request issued by saidfirst image forming apparatus; a judging section for judging, uponreceipt of every store request and based on said appended data, whethera present store request and a preceding store request were issued by asingle first image forming apparatus; and an accumulated image dataerasing section for, when said judging section judges both said presentand preceding store requests were issued by said single first imageforming apparatus, erasing only the image data accumulated andinformation related to the image data accumulated in said storagesection before said judgment was made.
 6. The image forming system asdefined in claim 5, wherein said second image forming apparatus furtherincludes a time measuring section for measuring a predetermined periodsince said transferred image data are stored in said storagesection,whereby, if said present and preceding store requests wereissued by said single first image forming apparatus, and when saidpresent store request was issued after said predetermined time haspassed, said accumulated image data erasing section erases saidaccumulated data, and when said present store request was issued withinsaid predetermined time, said accumulated image data erasing sectiondoes not erase said accumulated data.
 7. The image forming system asdefined in claim 5, wherein said second image forming apparatus furtherincludes:a reset section for erasing a content of said storage sectionin response to a reset signal; an inhibiting section for inhibiting saidreset section from erasing said stored image data and appended data insaid storage section.
 8. An image forming system comprising a firstimage forming apparatus, a second image forming apparatus, and atransmitting apparatus for connecting said first and second imageforming apparatuses for mutual image data transmission, wherein,(1) saidfirst image forming apparatus includes:a recording section for forming avisible image based on image data; a command input section for inputtingan action command; and a control section for transferring said imagedata from said first image forming apparatus to said second imageforming apparatus through said transmitting apparatus at a command,inputted through said command input section, to issue a store request tosaid second image forming apparatus to store said image data on behalfof said first image forming apparatus, and (2) said second image formingapparatus includes:a storage section for storing image data; an erasingsection for erasing only said stored image data and information relatedto said stored image data in said storage section; a transfer historydata managing section for managing transfer history data as to returningof said stored image data to said fist image forming apparatus sincesaid image data have been stored into said storage section; and acontrol section for storing said transferred image data from said firstimage forming apparatus into said storage section, and for performing,based on a return request issued by said first image forming apparatus,the operations of returning said stored image data to said first imageforming apparatus through said transmitting apparatus, and controllingerasing operations of said erasing section based on said transferhistory data, wherein said erasing section judges whether said storedimage data can be erased or not based on said transfer history data, anderases the image data judged as being erasable; wherein said transferhistory data indicate the number of times said image data stored in saidstorage section are returned to said first image forming apparatus; andwherein said erasing section determines erasing priorities of respectiveimage data stored in said storage section based on said number of timesof returning.
 9. The image forming system as defined in claim 8, whereinsaid erase section gives a higher priority to the image data which havebeen returned once than the image data which have never been returned.10. The image forming system as defined in claim 8, wherein said erasesection gives a higher priority to the image data which have beenreturned once than the image data which have been returned more thanonce.
 11. An image forming system comprising a first image formingapparatus, a second image forming apparatus, and a transmittingapparatus for connecting said first and second image forming apparatusesfor mutual image data transmission, wherein,(1) said first image formingapparatus includes:a recording section for forming a visible image basedon image data; a command input section for inputting an action command;and a control section for transferring said image data from said firstimage forming apparatus to said second image forming apparatus throughsaid transmitting apparatus at a command, inputted through said commandinput section, to issue a store request to said second image formingapparatus to store said image data on behalf of said first image formingapparatus, and (2) said second image forming apparatus includes:astorage section for storing image data; an erasing section for erasingonly said stored image data and information related to said stored imagedata in said storage section; a transfer history data managing sectionfor managing transfer history data as to returning of said stored imagedata to said fist image forming apparatus since said image data havebeen stored into said storage section; and a control section for storingsaid transferred image data from said first image forming apparatus intosaid storage section, and for performing, based on a return requestissued by said first image forming apparatus, the operations ofreturning said stored image data to said first image forming apparatusthrough said transmitting apparatus, and controlling erasing operationsof said erasing section based on said transfer history data, whereinsaid erasing section judges whether said stored image data can be erasedor not based on said transfer history data, and erases the image datajudged as being erasable; and wherein said transfer history dataindicate whether returning of said stored image data in said storagesection to said first image forming apparatus has ended or not, whereby,when said transfer history data indicates that the returning of saidimage data has ended, said erase section erases said image data.
 12. Animage forming system comprising a first image forming apparatus, asecond image forming apparatus, and a transmitting apparatus forconnecting said first and second image forming apparatuses for mutualimage data transmission, wherein,(1) said first image forming apparatusincludes:a recording section for forming a visible image based on imagedata; a command input section for inputting an action command; and acontrol section for transferring said image data from said first imageforming apparatus to said second image forming apparatus through saidtransmitting apparatus at a command, inputted through said command inputsection, to issue a store request to said second image forming apparatusto store said image data on behalf of said first image formingapparatus, and (2) said second image forming apparatus includes:astorage section for storing image data; an erasing section for erasingonly said stored image data and information related to said stored imagedata in said storage section; a transfer history data managing sectionfor managing transfer history data as to returning of said stored imagedata to said fist image forming apparatus since said image data havebeen stored into said storage section; and a control section for storingsaid transferred image data from said first image forming apparatus intosaid storage section, and for performing, based on a return requestissued by said first image forming apparatus, the operations ofreturning said stored image data to said first image forming apparatusthrough said transmitting apparatus, and controlling erasing operationsof said erasing section based on said transfer history data, whereinsaid erasing section judges whether said stored image data can be erasedor not based on said transfer history data, and erases the image datajudged as being erasable; wherein said transfer history data indicate atransfer time at which said stored image data in said storage sectionare transferred to said first image forming apparatus, whereby saiderase section erases said stored image data when said first imageforming apparatus has not issued another return request for said storedimage data within a predetermined time since said stored image data werereturned last time.
 13. The image forming system as defined in claim 12,wherein said erase section sets said predetermined time in accordancewith a processing rate of said first image forming apparatus.
 14. Theimage forming system as defined in claim 12, wherein said erase sectionsets said predetermined time in accordance with a request issuing cyclewhen more than one return request is issued for said stored image databy said first image forming apparatus.